The effect of BeF(x) and a natural toxin (jasplakinolide) was examined on the thermal stability of actin filaments by using differential scanning calorimetry. The phosphate analogue beryllium fluoride shifted the melting temperature of actin filaments (67.4 degrees C) to 83.7 degrees C indicating that the filaments were thermodynamically more stable in their complex with ADP.BeF(x). A similar tendency was observed when the jasplakinolide was used in the absence of BeF(x). When both the ADP.BeF(x) and the jasplakinolide bound to the actin filaments their collective effect was similar to that observed with ADP.BeF(x) or jasplakinolide alone. These results suggested that ADP.BeF(x) and jasplakinolide probably stabilize the actin filaments by similar molecular mechanisms.
The thermodynamic properties of the ternary Au-Cu-Sn system were determined with the electromotive force (EMF) method using a liquid electrolyte. Three different cross-sections with constant Au:Cu ratios of 3:1, 1:1, and 1:3 were applied to measure the thermodynamic properties of the ternary system in the temperature range between the liquidus temperature of the alloys and 1023 K. The partial free energies of Sn in liquid Au-Cu-Sn alloys were obtained from EMF data. The integral Gibbs free energy and the integral enthalpy at 900 K were calculated by Gibbs-Duhem integration. The ternary interaction parameters were evaluated using the Redlich-Kister-Muggianu polynomial.
Endothermic insects like honeybees and some wasps have to cope with an enormous heat loss during foraging because of their small body size in comparison to endotherms like mammals and birds. The enormous costs of thermoregulation call for optimisation. Honeybees and wasps differ in their critical thermal maximum, which enables the bees to kill the wasps by heat. We here demonstrate the benefits of a combined use of body temperature measurement with infrared thermography, and respiratory measurements of energy turnover (O2 consumption or CO2 production via flow-through respirometry) to answer questions of insect ecophysiological research, and we describe calibrations to receive accurate results.
To assess the question of what foraging honeybees optimise, their body temperature was compared with their energy turnover. Honeybees foraging from an artificial flower with unlimited sucrose flow increased body surface temperature and energy turnover with profitability of foraging (sucrose content of the food; 0.5 or 1.5 mol/L). Costs of thermoregulation, however, were rather independent of ambient temperature (13–30 °C). External heat gain by solar radiation was used to increase body temperature. This optimised foraging energetics by increasing suction speed.
In determinations of insect respiratory critical thermal limits, the combined use of respiratory measurements and thermography made possible a more conclusive interpretation of respiratory traces.
The partial and integral enthalpies of mixing of liquid ternary Ni-Sb-Sn alloys were determined along five sections x Sb/x Sn = 3:1, x Sb/x Sn = 1:1, x Sb/x Sn = 1:3, x Ni/x Sn = 1:4, and x Ni/x Sb = 1:4 at 1000 °C in a large compositional range using drop calorimetry techniques. The mixing enthalpy of Ni-Sb alloys was determined at the same temperature and described by a Redlich-Kister polynomial. The other binary data were carefully evaluated from literature values. Our measured ternary data were fitted on the basis of an extended Redlich-Kister-Muggianu model for substitutional solutions. Additionally, a comparison of these results to the extrapolation model of Toop is given. The entire ternary system shows exothermic values of Δmix H ranging from approx. -1300 J/mol, the minimum in the Sb-Sn binary system down to approx. -24,500 J/mol towards Ni-Sb. No significant ternary interaction could be deduced from our data.
Emerging trends in the interpretation of measurements of thermally stimulated conductivity, luminescence, and depolarization in organic polymers are reviewed, in the context of charge trapping and transport. Particular attention is given to the following: (1) the advantage of making simultaneous measurements on the same sample; (2) the determination of the forms of quasicontinuous distributions of trap activation energies; and (3) the use of thermally stimulated processes to monitor aging (degradation) of polymeric insulants in power distribution cables and hence estimate their economic service lifetimes
As an extension to our previous work carried out on the measurements of vapor pressures for heavy hydrocarbons we have performed a similar study for 11 primary alcohols. Our results are in good agreement with those published by Ambrose et al. in a fairly limited temperature range and, with a few small exceptions, with those reported by Smith and Srivastava. In all cases Antoine's equation leads to small deviations from measured values.Our motivation was twofold. Firstly the existence of an IUPAC project to study vapor-liquid equilibria for mixtures of primary alcohols with n-alkanes by correlating experimental determinations and group contribution methods; it is clear that the correlations require knowledge of the vapor pressures of pure substances. Secondly, the lack of data in the low vapor pressure field.RésuméLes auteurs ont amélioré un dispositif statique permettant de mesurer les tensions de vapeur de produits peu volatils dans le domaine 10−4 < P (kPa) < 1,5; 250 < T (K) < 460. Onze alcools primaires ont été étudiés allant de hexanol-1 au hexadécanol-1. Nos résultats expérimentaux sont en accord avec les quelques données publiées par Ambrose et coll. et à quelques exceptions près avec ceux de Smith et coll. Avec les autres auteurs l'accord est généralement mauvais.
The effects of temperature, pressure, and concentration on viscosity of aqueous LiI solutions were determined with a capillary-flow technique and compared with literature data and correlations. The data are interpreted with the extended Jones–Dole equation for strong electrolytes to calculate the viscosity A-, B-, and D-coefficients. Good agreement was found between derived values of the viscosity A- and B-coefficients and the results predicted by Falkenhagen–Dole theory of electrolyte solutions and calculated with the ionic B-coefficient data. It was found that the temperature coefficient, dB/dT > 0, for LiI(aq) is positive (structure-breaking ions). Physical meaning parameters V and E in the absolute-rate theory of viscosity and hydrodynamic molar volume Vk were calculated using present experimental viscosity data. The values of parameter E almost independent on temperature (around 11.1), while the values of parameter V monotonically decreasing as temperature increases. The Arrhenius–Andrade parameters (A and Ea/R) were calculated from measured viscosity data. The predicted capability and validity of the various theoretical models for the viscosity of electrolyte solutions were tested.
The crystal growth kinetics of Sb2S3 in (GeS2)0.2(Sb2S3)0.8 glass has been studied by DSC and optical microscopy. The linear growth kinetics of Sb2S3 has been observed in the temperature range 525 K ≤ T ≤ 556 K (EG = 295 ± 3 kJ mol−1). From the reduced growth rate plot (i.e., growth rate corrected for viscosity) as a function of supercooling it has been found that the most probable mechanism is interface controlled 2D nucleated growth. The DSC data, corresponding to the bulk sample under isothermal and non-isothermal, can be described by the Johnson–Mehl–Avrami equation for the kinetic exponent m ≅ 2.
A procedure was developed to calibrate the Calorimetry Sciences Corporation Models 5100 and 6100 Nano-DSCs to measure more precisely volumetric heat capacities of liquids and solutions. These calorimeters are small-volume, twin fixed-cell, power-compensation, differential-output instruments that can scan temperature upward or downward between 263 and 398 K at pressures up to 0.4 MPa. The calibration procedure leads to volumetric heat capacities that have a relative precision and accuracy of 3 × 10−6 to 5 × 10−5 for aqueous solutions at concentrations between ca. 0.001 and 1 mol kg−1. The Nano-DSCs operate on the principle that the volumetric heat capacity of a solution or liquid is proportional to the difference between the calorimetric outputs for two separate experiments: one when both the cells contain a reference liquid (usually water), and one when the reference cell contains the reference liquid and the sample cell contains the solution or some other liquid of interest. The volumetric heat capacity of the reference liquid must be known precisely and accurately at the temperatures and pressures of the experiment. The calibration constant is determined from measurements on a second reference liquid whose volumetric heat capacity is also known precisely and accurately: 1-mol kg−1 NaCl(aq). Results of calibration and other experiments are used as examples to illustrate the advantages of the calibration procedure described in this paper.
We investigated extensively equilibrium, nonequilibrium, and nonlinear aspects of the enthalpy relaxation in a supercooled liquid [Ca(NO3)2]0.4(KNO3)0.6. The equilibrium properties of relaxation, which are described in the framework of linear response theory, were determined from the frequency-dependent heat capacity measurements. The nonequilibrium and nonlinear aspects of relaxation were investigated by differential scanning calorimetry and time-domain dynamic calorimetry. It was found that the nonequilibrium relaxation can be fully accounted for in terms of the equilibrium one if the latter is properly extended, and that the successful extension of the equilibrium linear relaxation function must include both nonstationariness and thermorheological complexity. No evidence of genuine nonlinear enthalpy response, aside from the nonequilibrium effects, was seen in the time-domain dynamic calorimetric data, even when a temperature jump as large as 8 K was imposed.
The thermal behaviour of BaC2O4sd0.5H2O and BaCO3 in carbon dioxide and nitrogen atmospheres is investigated as part of a study about the thermal decomposition of barium trioxalatoaluminate. For this purpose thermogravimetry, differential thermal analysis, differential scanning calorimetry and high temperature X-ray diffraction were used. An infrared absorption spectrum of BaC2O4·0.5H2O was scanned at room temperature.At increasing temperature, in dry nitrogen, the hydrate water of BaC2O4· 0.5H2O is split off, followed by the oxalate decomposition. A part of the evolved carbon monoxide disproportionates, leaving carbon behind. At higher temperatures the latter reacts with barium carbonate, previously formed. Finally the residual solid barium carbonate decomposes into barium oxide and carbon dioxide.In dry carbon dioxide atmosphere an analogous dehydration occurs, followed by oxalate decomposition. Under these conditions the carbon formation is fully suppressed, and as a consequence no secondary reaction occurs. The barium carbonate decomposition is shifted to much higher temperatures, at a low rate in the solid phase, a strongly accelerated one at the onset of melting, and a moderated one when the melt is saturated with barium carbonate. The two phase transitions of BaCO3 are detectable in both atmospheres mentioned.
A comprehensive study of thermodynamic properties of 1,1′-biadamantane in different phase states has been carried out. The heat capacity of the compound in the condensed state was measured in two adiabatic calorimeters in the temperature range from 5 to 370 K and in a single-cup scanning calorimeter from 315 to 610 K. Two solid-to-solid phase transitions at 336.3 ± 0.3 K with = 1.154 ± 0.019 kJ mol−1 and 509.6 ± 0.5 K with = 1.30 ± 0.03 kJ mol−1, and fusion at Tfus ∼ 561 K were revealed in this temperature interval. It was found that 1,1′-biadamantane did not form plastic crystals. The thermodynamic functions of the compound in the crystalline state were derived. The saturated vapour pressure of 1,1′-biadamantane from 393 to 443 K was determined by the Knudsen effusion method:The sublimation enthalpy was obtained from the results of the effusion measurements: (417.8 K) = 109.1 ± 1.3 kJ mol−1, (298.15 K) = 113.8 ± 1.4 kJ mol−1. The complete set of fundamentals was compiled from experimental spectral data and results of calculations in terms of the density functional theory (B3LYP/6-31G*). The combustion enthalpy of C20H30, (298.15 K, cr) = −(11801.3 ± 7.3) kJ mol−1, was determined by the bomb-calorimetry method and the enthalpy of formation, (298.15 K, cr) = −(356.4 ± 7.8) kJ mol−1, was obtained. The thermodynamic properties of 1,1′-biadamantane in the ideal-gas state were calculated.
The effects of copper-1,10-phenanthroline combined with hyperthermia on human liver hepatoma cell line, Bel-7402 were studied. The effect was evaluated by the mean thermal power of the cells and total energy Q produced during the measurement period (35 h). It was found that the energy produced reduced after the treatment. Condensation of nuclear chromatin and apoptotic bodies can be observed from fluorescence microscope, which showed apoptosis occurs under the action of copper-1,10-phenanthroline combined with hyperthermia. The analysis by flow cytometry showed the proportion of apoptotic cells in the cell population increased. It indicates that the combination of hyperthermia and copper-1,10-phenanthroline has a synergetic effect on Bel-7402.
γ-Zirconium and γ-titanium phosphates containing organic diamine 2,9-dimethyl-1,10-phenanthroline and its in situ formed copper complex were studied by thermal analysis and physical measurements. All the derived materials show a layered structure and their interlayer distance is increased with respect to that of their precursors. Melting, simultaneous vaporization and oxidation, as well as a decomposition process take place in the pure diamine. After dehydration, all the intercalation materials undergo a two-step decomposition. The presence of the formed copper complex between the layers of the two ion-exchangers considered shows a destabilizing effect with respect to the intercalated diamine materials, resulting in a decrease of the decomposition temperatures and the activation energy of decomposition. The application of the isoconversional Ozawa–Flynn–Wall method substantially confirms the obtained results.
Coordination enthalpies and entropies of tripositive lanthanide ions with ligand trans-1,2-diaminocyclopentane-NNN′N′-tetraacetic acid (CPDTA) have been determined using a non-isothermal reaction calorimeter. From the experimental ΔHOc values and literature free-energy data the coordination entropies, ΔSOc, were calculated. Besides the expected irregular dependence of either ΔHOc or ΔSOc on r−1+, very significant correlations of ΔSoc with OLn as well as with ΔHOc have been observed.
The conditions of formation of Co(II), Ni(II), Cu(II) and Zn(II) benzene-1,2-dioxyacetates were studied and their quantitative compositions and solubilities in water at 295 K were determined. The IR spectra and X-ray diffractograms for the prepared complexes were recorded and their thermal decompositions in air were investigated. During heating, the hydrated complexes MC10H8O6·nH2O lose some crystallization water molecules in one or two steps, then decompose to the oxides, either directly (Zn) or with intermediate formation of the free metals (Co, Ni and probably Cu).
The temperature behaviour of various thermodynamic characteristics of the ideal gas-phase equilibrium mixture of gauche- and trans-1,2-difluoroethane has been studied on the basis of recently calculated molecular data. An interesting extremum temperature behaviour has been shown in a number of terms characterizing this isomeric interplay: among them, the isomerism contribution to heat capacity, whose maximum value is 3.39 J K−1 mol−1, is particularily distinctive.
The thermal behaviour of [Ba(C2H6O2)4][Sn(C2H4O2)3] used as a BaSnO3 precursor, and its phase evolution during thermal decomposition are described. The initially formed transient barium tin oxycarbonate phase disintegrates into BaCO3 and SnO2, reacting subsequently to BaSnO3. The existence of the intermediate oxycarbonate phase is evidenced by Fourier transformed infrared (FT-IR), X-ray powder diffraction (XRD) and electron energy loss spectroscopy (EELS (ELNES)) investigations.
The metal-ligand stability constants of the Ni(II), Co(II), Zn(II), Mn(II), Cd(II), Fe(III), UO2(II) and Ln(III) chelates of HipHT were determined in 75% (v/v) dioxane-water medium at 10, 20 and 30°C and μ = 0.1M(KNO3). The thermodynamic parameters for the proton-ligand and metal-ligand stability constants were obtained by the temperature coefficient method. The thermodynamic functions ΔG and ΔH of the complexes were analyzed in terms of the electrostatic (el) and non-electrostatic (non) components. The values of ΔHnon and ΔHel show a linear variation with the hardness and softness Eνn of the metal ion and with the heat of hydration ΔHh, of the metal ion, respectively. HipHT behaves as a diprotic tridentate (NNO) donor towards the metal ions, as inferred from the infrared spectra of its metal chelates.
This paper presents the results from a study of the thermal decomposition and thermal stability of NTO (3-nitro-1,2,4-triazol-5-one). Mass spectra of NTO are presented (electron impact 20 and 70 eV and chemical ionisation spectra). The large abundance of the molecular ion in these spectra shows that NTO is a more stable molecule than TNT or RDX. The data acquired for NTO is summarised as a proposed mass spectral fragmentation path. A number of laser ignition measurements were conducted. These measurements showed a strong pressure dependence, which clearly indicates a multiple phase (condensed and gas phase) ignition. The laser ignition measurements also showed that the sensitivity to ignition is slightly higher than that for TNT. The results of the LI-MS (laser induced mass spectrometry) method applied to NTO imply that the probable decomposition path is an elimination of NO2 followed by a breaking of the azole ring. The chemiluminescence (CL) method was used for determination of the activation energy and the frequency factor (Ea= 140 kJ and K0= 5 × 106s−1 in the temperature interval 100–140° C). Chemiluminescence data for RDX and TNT was acquired for comparison. The DSC spectrum of NTO showed only one peak, a very strong exothermic peak at 253°C. This study is complemented with some quantum mechanical calculations which were conducted in an attempt to verify the initial steps in the decomposition path and to explain the high stability of NTO. The results were computed with the mopac 6.0 code using the semi-empirical modified neglect of diatomic overlap (MNDO) method with the parametric method 3 (PM3) parameter set at the unrestricted Hartree-Fock level.
The thermal decomposition of NTO (3-nitro-1,2,4-triazol-5-one) was studied using DSC, TGA-MS, and ARC. The major gaseous products were identified, the approximate heat of decomposition was determined, and a chemical equation was suggested for the net reaction. It was found that the stability of NTO is sensitive to the thermal age of the sample. Kinetic analysis suggested an auto-catalytic mechanism. The thermal stability of NTO was compared with RDX (1,3,5-trinitro-1,3,5-triazacyclohexane) and its potential thermal hazard was assessed.
Preservation by low temperature vitrification is being developed for the cryopreservation of mammalian organs. The purpose is to avoid ice crystallization, which can cause damage during cooling or warming. With the high cryoprotectant concentrations being used, crystallization is easily avoided during cooling, but not during rewarming at practical warming rates. Assessment of the amount of crystallization occurring during warming is therefore necessary.1,3-butanediol is a good glass-former and a good cryoprotectant for red blood cells. Similar to 1,2-propanediol, it has already been used for the vitrification of erythrocytes. As a model, the crystallization kinetics of warming vitreous solutions are presented here for concentrations higher than 38% () 1,3-butanediol.Isothermal and continuous heating rate (CHR) experiments have been performed by differential scanning calorimetry and by direct optical observation using a cryomicroscope. For the isothermal method, the Johnson-Avrami equation and its second derivative were used for thermal analysis. For the CHR approach, the isoconversional method was used, assuming always a Johnson-Avrami variation for the crystallization fraction. The calorimetry results were then compared with the cryomicroscopy observations, allowing a determination of the exponent n. The isothermal approach gives higher calculated parameters than the CHR approach. By the isothermal approach, the Avrami exponent n varies between 2.5 and 3 and the “ctivation energy” E★ decreases from 16.9 to 11.5 kcal mol−1. By the CHR approach, n increases from 1.8 to 2.5 and the various methods used give similar results for E★, with the same variations in polyalcohol concentrations as with the isothermal method. With the isothermal method, a break point is observed for both E☆ and n, determined from calorimetry, at 44–46% 1,3-butanediol. This corresponds to a change in the kinetics of the crystallization observed by cryomicroscopy.
Densities and heats of mixing for the ternary system 2-butanol+1,3-dioxolane+n-hexane have been measured at atmospheric pressure at the temperatures of 298.15 and 313.15 K. Excess molar volumes and excess molar enthalpies have been calculated from experimental data and fitted by the Redlich–Kister equation for ternary mixtures. The ERAS model has been used to calculate excess molar properties of the ternary mixture from parameters obtained from the constituent binary mixtures.
The silylant precursor agent 3-glycidoxypropyltrimethoxysilane was covalently anchored onto a silica gel surface followed by propane-1,3-diamine molecule incorporation using a heterogeneous route (SiHT). On another series, the precursor agent was previously reacted with diamine to give the silylant agent in homogeneous condition, before immobilization (SiHM). The degrees of immobilization were 0.80 and 1.53 mmol g−1 for SiHT and SiHM, respectively. Both grafting surfaces were employed to extract the divalent cations nickel, copper, cobalt and zinc from aqueous solutions. This cation/nitrogen interactive process was calorimetrically followed to give exothermic enthalpy, negative free Gibbs energy and positive entropy values. These favorable thermodynamic data are more pronounced for copper on both surfaces, with a higher tendency for SiHM, due to the larger amount of available nitrogen atoms in the pendant chain covalently attached to the inorganic silica backbone.
The enthalpies of solution of 1,3-dimethylpropyleneurea in ordinary (H2O) and heavy (D2O) water were measured at (278.15, 283.15, 288.15, 298.15, and 313.15) K and atmospheric pressure. Standard enthalpies and heat capacities of solution (hydration), along with D2O–H2O solvent isotope effects on the quantities studied, were computed. The enthalpies of solution as well as corresponding solvent isotope effects were found to be negative and decreasing in magnitude with increasing temperature. It was established that the hydration (mainly of a hydrophobic type) is enhanced in D2O and on going from 1,3-dimethylethyleneurea (1,1,3,3-tetramethylurea) to 1,3-dimethylpropyleneurea, whereas the enthalpy-isotope effects become less appreciable in the latter case.
A thermoanalytical study of the aminoderivatives 1-amino-2,4,6-trinitrobenzene (PAM), 1,3-diamino-2,4,6-trinitrobenzene (DATB), 1,3,5-triammo-2,4,6-trinitrobenzene (TATB), 2,2',4,4',6,6'-hexanitrodiphenylamine (DPA), 2,2',4,4',6,6'-hexanitrooxanilide (HNO) and 2,4,6-tris(2,4,6-trinitrophenylamino)-1,3,5-triazine (TPM) has been carried out. In the case of TATB, an endothermic change was found in the temperature region 321–326°C by means of DSC. By comparing the melting points of 1,3,5-trinitrobenzene, PAM and DATB, and of the endothermic change of TATB, with the melting points of the derivatives 1,3,5-triazine derivatives, which are structural analogues, it can be deduced that this temperature region corresponds to the melting point range of TATB.The stability of all the compounds being studied was specified by means non-isothermal thermogravimetry (TGA). Linear dependences were found between the positions of the DTG peaks, or of the TGA onsets, and the weights of the samples. Analysis of the dependences gave results which were correlated with the rate constants of the isothermal thermolysis of the compounds and with their temperatures of explosion. From this analysis the Arrhenius parameters E = 153.3 kJ mol−1 and log A = 11 were determined for the DPA thermolysis in the temperature region 200–300°C.
We apply differential scanning calorimetry (DSC) to measure the kinetics of the β→δ solid–solid phase transition of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine, HMX. Integration of the DSC signal gives a direct measurement of degree of conversion. Data is analyzed by first-order kinetics, the Ozawa method, and isoconversional analysis. The range of activation energies found in this work, centering around 500 kJ/mol, is much higher than previously reported values by Brill and co-workers [AIAA J. (1982)], 204 kJ/mol , and Henson et al. and Henson and co-workers [B. Henson, L. Smilowitz, B. Asay, P. Dickson, Thermodynamics of the beta to delta phase transition in PBX-9501, in: Proceedings of American Physical Society Topical Group on Shock Compression of Condensed Matter, American Institute of Physics, Atlanta, GA, 2001; L. Smilowitz, B. Henson, J. Robinson, P. Dickson, B. Asay, Kinetics of the beta to delta phase transition in PBX-9501, in: Proceedings of American Physical Society Topical Group on Shock Compression of Condensed Matter, American Institute of Physics, Atlanta, GA, 2001; P.M. Dickson, B.W. Asay, B.F. Henson, C.S. Fugard, J. Wong, Measurement of phase change and thermal decomposition kinetics during cookoff of PBX-9501, in: Proceedings of American Physical Society Topical Group on Shock Compression of Condensed Matter, American Institute of Physics, Snowbird, UT, 1999], 200 kJ/mol . We discuss possible reasons for the higher activation energies measured here but do not identify the cause.
Four series of unsymmetrical 1,4-phenylene-bis-(4-substituted benzoates) were prepared in which one substituent is a terminal alkoxy group with a number of carbon atoms kept constant (at n=6, 8, 14, and 16) while the other substituent (X) alternatively changed from CH3O, CH3, Cl, NO2, CN, and CnH2n+1O. Compounds prepared were characterized by infrared spectroscopy and their mesophase stabilities investigated by differential scanning calorimeter (DSC) and polarized-light microscope. The results were discussed in terms of mesomeric and polarizability effects. In all the four series, the mesophase–isotropic transition temperatures (Tc) were successfully related to the polarizability anisotropy of bonds to the small compact substituent, X.
Viscosities η of dilute solutions of n-propylamine, n-butylamine, di-n-propylamine, di-n-butylamine, triethylamine, tri-n-propylamine, and tri-n-butylamine in 1,4-dioxane and oxolane (tetrahydrofuran) have been measured at 303.15 K. The specific viscosities and viscosity deviations Δη have been calculated. The values of and Δη for alkylamine solutions are negative in dioxane while positive in oxolane, and their magnitude increases with the increase in concentration of alkylamine. The values of excess Gibbs energy of activation ΔG*E of viscous flow, based on Eyring's theory of absolute reaction rates, are negative for alkylamine solutions in 1,4-dioxane, while positive for alkylamine solutions in oxolane solutions. The results have been analyzed in terms of Herskovits and Kelly equation and Nakagawa equation. The values of viscosity increment ν in Herskovits and Kelly equation and the coefficient B′int in Nakagawa equation are negative for the investigated alkylamine solutions in dioxane, while opposite is the case for oxolane.
The Arrhenius kinetics of decomposition of the nitramine explosive 1,4-dinitrofurazano[3,4,b]piperazine (DNFP) and the less energetic parent amine furazano[3,4,b]piperazine (FP) were determined by isothermal TGA and from the rate of change of selected vibrational modes in the IR spectra. For DNFP, Ea = 136 kJ and log A = 15.5 min−1. The IR spectra show that NNO2 homoloysis is the dominant initial reaction. For FP, Ea = 202 kJ and log A = 22.1 min−1. The value of Ea is the same as the NO bond strength of the furazan ring.
Heat of mixing data for the ternary liquid system n-butylamine-1,4-dioxane-ethanenitrile at 298.15 K are reported along with data for the constituent binary systems. Different expressions published in the literature were used to predict excess enthalpies from the corresponding binary data. The empirical correlation of Tanaka and Tamura gave the best prediction for this system.
Crystalline title compound (1) prepared from aqueous solution of theophylline and 1,4-diaminobutane has been structurally and thermally characterized. Both the two-step TG decomposition curve and elemental analysis of the hexagonal crystals show that it consists of theophylline and 1,4-diaminobutane in 2:1 molar ratio. Actually, presence of one type of both theophyllinate anions and 1,4-diammoniumbutane dication have been indicated by FTIR spectroscopy. The molecular structure of lattice compound (1) has been determined by single crystal X-ray diffraction, where the hydrogen positions have been obtained from differential Fourier maps. It has confirmed that the crystal is really built up from these ionic constituents bound together with an extensive net of hydrogen bonds. The coupled TG-FTIR analysis of the evolved gases has revealed that the diamine is released as a whole molecule in the first decomposition step. Clathrate 1 and the proton migration in it might serve as a structural model of solid aminophylline whose crystal structure is still unknown.
TNAD, a polycyclic nitramine, has been studied with regard to the kinetics and mechanism of thermal decomposition and also the morphology and the gaseous products evolved therefrom, using thermogravimetry (TG), differential thermal analysis (DTA), infrared (IR) spectroscopy, differential scanning calorimetry (DSC) and hot stage microscopy. The IR spectra of TNAD have also been recorded and the bands assigned. The kinetics thermolysis have been followed by isothermal TG. The best linearity (with a correlation coefficient of 0.9859) has been obtained for the three dimensional diffusion controlled equation. The activation energy has been found to be 156.48 kJ mol−1 and is 13.77. The effect of a series of additives incorporated to the extent of 5%, on the initial thermolysis of TNAD, has also been studied. Evolved gas analysis by IR spectroscopy showed that CO2, NO2, NO and N2O are produced in larger amounts than CO and HCN. The cleavage of the NN bond appears to be the primary step in the thermolysis of TNAD.
The heats of protonation of 12-(2′-hydroxy-benzyl)-1,4,7,10-tetraazacyclotridecane-11,13-dione (HTADO) have been determined in aqueous solution at 25 ± 0.1°C and I = 0.1 mol dm−3 KNO3 by conduction calorimetry. The heats of formation of the binary complex compound of this ligand with Cu(II) and the ternary complex compounds of this ligand with Cu(II)-5-substituted phenanthrolines have also been determined under identical conditions. By utilizing the calorimetric data, the heats of formation of the ternary complex compounds Cu(II)-α-aminoacids-HTADO have been evaluated through “overall calculation”. Some linear enthalpy relationships have been found between the heats of protonation of the ligands and the heats of formation of the ternary complex compounds.
A new adiabatic detonation calorimeter has been designed. The maximum amount of sample tested is 50 g and the precision of measurement is near 0.3%. The pellet can be detonated in vacuum or under nitrogen. The value of the heat of detonation of 1,5-diazido-3-nitrozapentane tested by this device is 3538 J g−1.
Vapour pressure measurements of high boiling point hydrocarbons (C10-C18n-alkanes and n-alkylbenzenes) were carried out in the range: 10−1 < P0 < 10 mm Hg, 50 < t0 < 250°C.The gas-saturation method for measuring low vapour pressures was used.Trial was made of several equations for the representation of the vapour pressure-temperature relationship. The best extrapolation is given by the Scott and Osborn equation. The experimental data are well correlated by this equation.RésuméLes auteurs ont mesuré la tension de vapeur (P0) de divers hydrocarbures lourds n-alcanes et n-alkylbenzènes (C10–C18) dans le domaine: 10−2 < P0 <10 mm Hg, 50 < t0 < 250° C.L'appareil utilisé est basé sur la méthode de saturation de gaz inerte avec analyse chromatographique. de la phase gazeuse.Après une étude critique des différentes équations de lissage des tensions de vapeur, les auteurs ont choisi l'équation de Scott et Osborn. Cette dernière permet une extrapolation des données de la littérature dans notre gamme de mesures.Pour les n-alcanes (excepté le C18), les résultats expérimentaux et les valeurs extrapolées de la littérature sont en très bon accord (écart relatif sur les pressions de quelques pour cent). Dans le cas des n-alkylbenzènes, les écarts sont nettement plus grands (de 10 à 20%).
Equipment is described for measurement of low vapor pressure, P0, in the range: 3 Pa < P0 <1000 Pa; 50°C < t < 250°C. A possible error of 1% in P and ± 0.02°C in T were estimated.The inert gas-saturation method was used. The vapor pressure was determined by measuring the saturated vapor concentration in the inert gas using a gas chromatograph. The detector chromatograph was calibrated for the material studied. External calibration was chosen and a special syringe was designed and built for this purpose.The apparatus was designed with the following features: (1) by adapting a sample injection valve the gas phase analysis is simple and very accurate; (2) the use of a differential pressure transducer permits accurate measurement of inert gas pressure.The partial vapor pressure, Pi, was measured for several total pressures, P. The extrapolation to P = 0 of the plot log Pi, vs. P gave the partial vapor pressure of pure substance. This method was derived from thermodynamic considerations (Poynting effect and non-ideality of gas phase).RésuméLes auteurs décrivent un dispositif permettant la mesure de faibles pressions de vapeur (dans le domaine 3–1000 Pa). La méthode consiste à entraîner les vapeurs du corps étudié par un gaz inerte. La tension de vapeur de celui-ci est déterminée en mesurant sa concentration par chromatographie. L'originalité du montage réside en la présence d'une boucle d'injection qui permet une analyse chromatographique très précise. Les résultats expérimentaux obtenus mettent en évidence l'influence de la correction de Poynting et de la non-idéalité de la phase vapeur. L'appareil a été testé sur le dodécane: l'extrapolation des résultats expérimentaux à une pression nulle de gaz entraineur conduit à des valeurs en parfait accord avec les données de la littérature ou avec eelles obtenues par les auteurs au moyen d'un isoténiscope.
Heat capacities of single crystal of κ-(BEDT-TTF)2Cu(NCS)2, which is known as an organic superconductor with Tc = 9.5 K, were measured with a recently constructed 3He-calorimeter of a relaxation type. A large heat capacity jump of about ΔCpT−1 = 65 mJ K−2 mol−1 was observed in association with the superconductive transition. The characteristic behavior of the thermal anomaly is compared with the previous results reported. Only slight change was found between the heat capacity peaks for the slowly cooled and rapidly cooled samples. This demonstrates that the degree of disorder left in the cooling process is not so serious in this material.
The application of used engine lubricating oils for further service was evaluated on the basis of chemical and thermal analyses. The most substantial chemical variables, namely kinematic viscosity at 323 and 373 K, flash point and content of foreign solids and oxide ash were determined. The two groups of thermal variables were determined based on the TG and DTG curves. The temperatures for onset, end and successive mass losses were read from the TG curves, whereas the temperature range of DTG peak, peak temperature, peak height and peak width at a half of peak height were read from the DTG curves. To find the relation between the chemical and thermal variables, regression and principal component (PCA) analyses were applied. Good linear relations were found between majority of chemical and thermal variables. The results of PCA indicate that the TG and DTG techniques are very useful in defining the degree of wear of used lubricating oils.
Densities and refractive indices of the binary mixtures of propan-1-ol with n-undecane and with n-dodecane at 288.15, 298.15, 308.15 and 318.15 K have been determined as a function of the concentration of the n-alkanol. The results were employed in order to determine the mean thermal expansion coefficients, both of the pure compounds and of their mixtures by using, on the one hand, the basic expression α= −(∂ ln ϱ/∂t)p and, on the other, certain empirical expressions arising from the definitions of specific refraction given by Gladstone and Dale, Lorentz and Lorenz and Eykman. The results obtained for αE are also discussed.
The combination of DTA, with thermogravimetric analysis is a method widely used in a wide range of temperature. However DTA measurements are qualitative and sometimes are issued from investigation of a sample different from the thermogravimetric one. On the other hand, if the sensor is supported by the balance - simultaneous measurement - the thermogravimetric sensitivity becomes very poor.A real improvement is obtained when combining the Differential Scanning Calorimeter SETARAM DSC 111 with the very sensitive symmetrical microbalance B 111 (limit of detection : 1 μg). The crucibles hanging on the balance are centered without mechanical contact in the DSC tubes crossing the calorimeter.
A perfluoro-sulphonate-ionomer membrane (Nafion-117), incorporated with inorganic ion exchanger (IIE), was evaluated using thermogravimetric analysis and FT-IR spectroscopy to ascertain its thermolytic degradation behavior. The two-step decomposition shown by derivative scans in the Nafion–polyantimonic acid composite was studied by obtaining FT-IR spectra of thermally treated specimens under dynamic conditions up to 200°, 350° and 400°C. Similar studies were carried out for Nafion–zirconium phosphate and Nafion–zirconium oxide composites. Incorporation of IIE invariably decreased the thermal stability of the perfluoro polymer matrix of Nafion. However, the decomposition patterns of –SO3H groups remained unaffected. Comparative studies of the TGA and DTA scans of these composites show presence of water of crystallization in the incorporated IIEs.
Latent heat storage systems, using phase change materials (PCMs), present the advantage of a high storage density at nearly constant temperature. They offer intrinsic advantages for heat storage in combination with steam as heat transfer fluid. Important applications of these storage systems are the areas of solar industrial process heat supply and heat recovery in industrial batch processes.
The presented work aims to identify the most suitable PCMs, according to the studied temperature range (120 to 150 °C) and is based both on literature review and thermal analysis measurements. The thermal behaviour of eleven potential storage materials was studied by means of thermogravimetry (TG) and differential scanning calorimetry analysis (DSC), coupled with a quadrupole mass spectrometer (QMS). The paper emphasizes the importance of the measurement conditions on the results. In particular the impacts of the type of crucible (open/closed), the atmosphere (N2, N2/O2) and the cycling stability are presented.
In this work, dehydration of Na3PO4·12H2O has been studied dynamically in detail by thermo-Raman spectroscopy. The dehydration was observed in the temperature range from 30 to 200°C. Spectral variation could distinguish six characteristic spectra of different hydrated species. The thermo-Raman intensity for the stretching bands of H2O showed four distinct steps of dehydration with Na3PO4·12H2O, Na3PO4·8H2O, Na3PO4·7H2O, Na3PO4·6H2O and Na3PO4·0.5H2O as the compositional species. The differential thermo-Raman intensity thermogram indicated the possibility of the existence of a new hydrated intermediate species Na3PO4·4H2O during the dehydration. The first four steps of dehydration occurred below 84°C and the last step of loosing 0.5 H2O could not be detected. The results of TG measurement showed only two stages of dehydration.
Real-time multiple-ion detection trend analysis mass spectrometry has been employed to study the temperature-programmed decomposition of AlNH4(SO4)2 · 12H2O in the temperature range 300–1200 K. Significant correlations are established with certain non-isothermal solid state kinetic rate expressions through the use of fraction release plots obtained from Evolved Gas Analysis Mass Spectra (EGA-MS). The EGA mass spectra clearly resolve the dehydration stage and various other stages associated with the thermal decomposition. The dehydration step is concomitant with stage I of a three-stage ammonia release followed by the final decomposition of Al2(SO4)3. These stages are found to comply with models based on random nucleation and diffusion approaches. A change in rate-governing mechanism was noticed with increase in the heating rate for the dehydration step. Relevant Arrhenius parameters such as the activation energy and pre-exponential factor were determined for all the decomposition stages. The ultimate product resulting from the decomposition was confirmed as γ-alumina by X-ray diffraction studies.
Gas exchange measurements by means of indirect calorimetry can be used to calculate quantitative substrate oxidation. The results represent average net oxidation values (substrate disappearance rate), but they cannot describe the dynamics of the oxidation processes. Breath test measurements with substrates labelled with 13C provide an attractive tool to describe the dynamics of oxidation processes, and may in combination with indirect calorimetry refine estimation of substrate oxidation. The objective of our investigation was to estimate oxidation of 1-13C labelled leucine in mink in response to feeding and fasting. Twelve 1-year-old male mink (Mustela vison) were measured in each five consecutive periods by means of indirect calorimetry and simultaneous breath test. In Periods 1, 3 and 5, each lasting 3 days, the animals were fed ad libitum and Periods 2 and 4 were fasting periods, each of 48 h. In Periods 1 and 5 all animals were fed a diet with a high quality fish meal (FISH; n=12), while in Period 3 half of the animals received the FISH diet (n=6) and the other half a diet with soy protein concentrate (SOY; n=6) as main protein source. An intraperitoneal injection of 1-13C-leucine was given before measurements started and expired air was then sucked out of the respiration chamber and collected into breath bags at frequent intervals until 5.5 h after the start of measurements. The ratio of 13C/12C was measured by means of an IRIS infrared analyser and results are reported in terms of delta over baseline (DOB) values. There was no significant effect of dietary treatment group, but the interaction between treatment group and sampling time was significant (P=0.02), peak DOB values being recorded 70–135 min after injection in FISH animals, and 70–120 min in SOY animals. The effect of period was significant (P=0.03), values generally being lower during fasting, indicating a lower rate of leucine oxidation. It was concluded that the present results clearly demonstrate differences in rate of oxidation of leucine between fed and fasted animals.
A linear relationship is shown to exist between the Arrhenius parameters E and log A of the initial stage of the non-autocatalysed, low-temperature thermolysis and the 13C and 15N chemical shifts of six nitramines. The existence of this relationship is interpreted from the point of view of the primary fragmentation in the thermolysis of the nitramines, i.e. homolysis of the N-NO2 bond. A linear relationship is also found between the heat of explosion (represented as the square of the detonation velocity and the 15N chemical shift of the nitro groups of four of the nitramines and as well as the 13C chemical shift in the derivatives with the methylene-nitramine grouping within their molecules.
The isothermal dehydration of magnesium oxalate dihydrate has been studied under various pressures of water vapour by use of a thermogravimetric balance. The rate of dehydration was found to be dependent upon the water vapour pressure.The reaction rate at temperatures below 124°C decreases sharply with an increase in water vapour pressure up to 0.5 mm Hg. With further increase in pressure an increase in rates is observed; this rises to a maximum and then falls again as the pressure is increased. The limitation of this phenomena to a limited temperature range is shown in the case of magnesium oxalate dihydrate. Above 124°C the initial fall in rate is not observed, the rate rises with increasing pressure from vacuum to a maximum and the falls. X-ray diffraction studies indicated that the anhydrous product prepared in the second region where a decrease of rate of dehydration occurred was crystalline but the sample dehydrated under vacuum or in the first region produced an amorphous anhydrous salt. A compensation effect is demonstrated with plots of the activation energy against the logarithm of the pre-exponential term in the Arrhenius equation.
A new high temperature calorimeter, based on modifications and improvements to the commercial integrated heat flux Setaram design is described. In this unit thermal effects are measured differentially along the vertical axis of the calorimeter. Performance was tested at 1473 K through the measurement of the enthalpies of formation of intermetallic compounds, using high temperature mixing calorimetry.
For many years, calorimetry has been recognized as a powerful and universal tool for monitoring chemical and biological processes. A laboratory-scale reaction calorimeter (RC1, Mettler–Toledo), initially developed for chemical reaction studies with a sensitivity of 100–150 mW/l, has been improved to enable the monitoring of very low heat production rates (<10 mW/l). A major limitation to successful process control, has been the inability to achieve real-time quantitative calorimetry. This is in part due to the operating principle of the RC1, in which the measured heat signal is calculated from the temperature difference between the reaction mass and the jacket oil and the heat transfer coefficient (UA). The latter frequently varies during a reaction, particularly a bioreaction, due to changes in volume, viscosity and cell density, and is difficult to determine accurately during the process.