Thermodynamic properties of montechellite

A thermochemical study of natural calcium and magnesium orthosilicate ─ monticellite (Ca1.00Mg0.95)[SiO4] (Khabarovsk Territory, Russia) was carried out on the Tian-Calvet microcalorimeter. The enthalpy of formation from the elements fHоel(298.15 K) = -2238.4 4.5 kJ / mol was determined by the method of high-temperature melt solution calorimetry. The enthalpy and Gibbs energy of formation of monticellite of the theoretical composition of CaMg[SiO4] are calculated: fH0el(298.15 K) = -2248.4 4.5 kJ/mol and fG0el(298.15 K) = -2130.5 4.5 kJ/mol.

Natural kaersutite: ftir, raman, thermal and thermochemical investigations

A thermochemical study of the natural oxo-amphibole ─ kaersutite Na0.4K0.3(Ca1.6Na0.4)(Mg2.9Fe0.82+Al0.7Ti0.6Fe0.53+)[Si6.1Al1.9O22](OH)0.2O1.8.(alkaline basalts of Mongolia) was performed on a Tian-Calvet microcalorimeter. The enthalpy of formation from the elements ∆fH el0(298.15 K) = – 12102 ± 16 kJ/mol) was obtained by the method of high-temperature melt solution calorimetry. The entropy, enthalpy and Gibbs energy of the formation of the end-members of the isomorphic series kaersutite NaCa2Mg3TiAl[Si6Al2O22]O2 – ferri-kaersutite NaCa2Mg3TiFe3+[Si6Al2O22]O2 were estimated.

Thermochemical study of sodium and sodium-calcium amphibols

A thermochemical study of six natural sodium and sodium-calcium amphiboles was carried out using the high-temperature melt solution calorimetry on a Tian-Calvet microcalorimeter. The enthalpies of formation from the elements have been obtained for arfvedsonites: K0.5(Na1.5Ca0.5)(Mg4.0Fe0.93+Al0.1)[Si8.0O22](OH)2 (Inaglinsky Massif, Central Aldan, Russia) (-11626.6 ± 8.9 kJ/mol), (Na0.5K0.1)(Na1.6Ca0.4)(Mg3.6Fe0.42+Fe0.83+Al0.2)[Si8.0O22](OH)2 (Khibiny Massif, Kola Peninsula, Russia) (-11520.8 ± 14.6 kJ/mol) and (Na0.7K0.3)Na2.0(Fe4.02+Fe0.63+Mn0.1Ti0.1Al0.2)[Si8.0O22](OH)2 (Katuginskoe deposit, Transbaikalia, Russia) (-11384.7 ± 17.1 kJ/mol); for riebeckites: Na2.0(Mg2.5Fe0.52+Fe1.53+Al0.5)Si8O22(OH)2 (Kumula deposit, Central Kazakhstan) (-10791.0 ± 10.1 kJ/mol) and Na2.0(Mg0.9Fe2.12+Fe1.93+Al0.1)[Si8O22](OH)2 (Krivoy Rog, Ukraine) (-10260.8 ± 10.9 kJ/mol) and richterite (Na0.7K0.3)(Ca1.2Na0.8)(Mg4.6Fe0.42+)[Si7.8Al0.2O22](OH)2 (Kovdorsky Massif, Kola Peninsula, Russia) (-12154.2 ± 9.7 kJ/mol). The values of the standard entropies, enthalpies, and Gibbs energies of formation are estimated for the end members of isomorphic series: arfvedsonite – magnesioarfvedsonite, riebeckite – magnesioriebeckite and richterite – ferrochichthite.

Electomagnetic absorption of composites based on epoxy resin and metallic iron nanoparticles

The heat losses originated from the electro-magnetic absorption in magnetic epoxy-based composites with embedded metallic iron nanoparicles were studied by Calvet microcalorimetry. Iron magnetic nanoparticles (MNPs) were synthesized by electrical explosion of wire (EEW) method; they were non-agglomerated, spherical in shape and had a weight average diameter 85 nm. Composites based on the cured epoxy-dian resin contained MNPs in weight content varying from 10% up to 70% . To study the heat loss in alterating magnetic field commercial Calvet microcalorimeter was equiped by two coils in the serial connection placed in the calorimeter cells; one of the coils contained a sample of composite the other was a reference. The electromagnetic adsorption was studied in the alternating magnetic field up to 1700 A /m in 67 – 214 kHz frequency range. The measured values of the specific power losses revealed linear dependence on iron MNPs content in composite and non-linear increasing function of the field frequency.

Thermochemical Properties of Dissolution of Nitroguanidine in Dimethyl Sulfoxide and N,N-Dimethylformamide

Abatract. The enthalpies of dissolution for nitroguanidine (NQ) in dimethyl sulfoxide (DMSO) andN,N-dimethylformamide (DMF) were measured using a RD496-2000 Calvet microcalorimeter at 298.15 K. Empirical formula for the calculation of the enthalpies of dissolution (ΔdissH) was obtained from the experimental data of the dissolution processes of NQ in DMSO and DMF. The corresponding kinetic equations describing the dissolution processes were dα/dt=10-1.49(1-α)0.94for the dissolution of NQ in DMSO and dα/dt=10-1.59(1-α)0.90for the dissolution of NQ in DMF.

Comparative Study of Microcalorimetric Behavior of Escherichia coli, Proteus mirabilis and Klebsiella pneumoniae

To analyze the microcalorimetric behaviour of Escherichia coli, Proteus mirabilis and Klebsiella pneumoniae, and to test the prospective use of microcalorimetry in the early diagnosis of infections by enterobacteria. For our experiments we used cultures of E. coli, P. mirabilis and K. pneumoniae. For the experimental setup, we used a Calvet microcalorimeter with the constant temperature of 309 K inside. Using the measured difference of heat power generated by the cells over time, we obtained growth graphs of the three bacterial species grown at different densities. The generated curves have characteristic plot that repeats for each bacterial species at all the concentrations studied. We observed an inversely proportional relationship between inoculum size and the time until signal detection; the smaller inoculum, the longer time for the signal detection. In all conducted experiments, even with low number of bacteria (10 CFU/ml) as inoculum, we could identify bacterial growth in the sample within 8 hours. Microcalorimetry could be an efficient technique used for the early detection and identification of enterobacteria in a culture medium.

PID-Based Thermal Control in Heat Conduction Micro-Calorimeters

Strategies based on the principle of heat flow and temperature control were implemented, and experimentally tested, to increase the sensitivity of a Tian-Calvet microcalorimeter for measuring heats of adsorption. Here, both heat-flow and temperature control schemes were explored to diminish heater-induced thermal variations within the heat sink element hence obtaining less noise in the baseline signal. PID controllers were implemented within a closed-loop system to perform the control actions in an calorimetric setup. The experimental results demonstrate that the heat flow control strategy provided a better baseline stability when compared to the temperature control. A modified control strategy is then suggested to maintain a stable core temperature and signal noise level in the system.

Excess molar enthalpies of mixtures of methyl derivatives of polyethylene glycol with 1-alkanol at 298.15 K and 101.3 kPa

Excess molar enthalpies (H E) of the binary mixtures containing tetraethylene glycol dimethyl ether (TEGDME) or polyethylene glycol 350 monomethyl ether with a 1-alkanol (1-propanol, 1-butanol, or 1-pentanol) at 298.15 K and atmospheric pressure were measured using a Calvet microcalorimeter. All the H E experimental values were positive and increase as the 1-alkanol length increases. The results are discussed qualitatively in terms of molecular interactions. The UNIFAC and DISQUAC group contribution models have been used to compare the predicted and the experimental values.Key words: excess enthalpy, 1-alkanol, polyether, binary system.

Heats of Adsorption of Aliphatic Alcohols on α-Al2O3 at 25–200°C. II. Variations with Chain Length

The adsorption of the first five members of the aliphatic alcohol series on α-Al2O3 has been studied at 25–200°C by means of a heat-flow Calvet microcalorimeter (moderately high temperature). At very low coverage and at 25°C, the values of the differential heats of adsorption of the different alcohols were very high (250–200 kJ/mol) and were apparently independent of the chain length. However, at average coverage, the chain length of the alcohol began to influence both the values and the trends in the differential heats of adsorption of the various alcohols on α-Al2O3. Finally, at high coverage, it was found that the incorporation of each additional –CH2–group in the homologous series led to a decrease in both the integral heat of adsorption and the amount of alcohol adsorbed according to the series MeOH > EtOH > 1-PrOH > 1-BuOH > 1-PeOH. Increasing the temperature led to an increasing dependence of the differential heat on the chain length of the alcohol. In addition, from measurements of the thermokinetic parameters for the heat emission peaks for the adsorbed alcohols, it has been deduced that all five aliphatic alcohols studied adsorb on to an α-Al2O3 surface in an open-chain perpendicular fashion.