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Abstract  

Heat capacities of U1–yLayO2 were measured by means of direct heating pulse calorimetry in the temperature range from 300 to 1500 K. An anomalous increase in the heat capacity curve of each sample was observed similarly to the case of U1–yGdyO2, found recently in our laboratory. As the lanthanum content of U1–yLayO2 increased, the onset temperature of an anomalous increase in the heat capacity decreased and the excess heat capacity increased. The enthalpy of activation (Hf) and the entropy of activation (Sf) of the thermally excited process, which cause the excess heat capacity were obtained to be 2.14, 1.63 and 1.50 eV and 39.4, 34.2 and 31.8 J·K–1·mol–1 for U0.956La0.044O2, U0.910La0.090O2 and U0.858La0.142O2, respectively. The values at zero La content extrapolated by using the data of Hf and Sf for U1–yLayO2 were in good agreement with the experimental values of undoped UO2 so far reported, similarly to the case of Gddoped UO2. The electrical conductivities of U1–yLayO2 (y=0.044 and 0.142) were also measured as a function temperature. No anomaly was seen in the electrical conductivity curve. It may be concluded that the excess heat capacity originates from the predominant contribution of the formation of oxygen clusters and from the small contribution of the formation of electron-hole pairs.

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Abstract  

The 'extremely diluted solutions', anomalous solutions prepared through the iteration of a process of dilution and succussion, have been studied with the aim of obtaining information about the influence of the preparation method on the water structure of the solutions. We measured the heats of mixing of basic solutions with such 'extremely diluted solutions', and their electrical conductivity, comparing with the analogous heats of mixing, electrical conductivity of the solvent. We found some relevant exothermic excess heats of mixing, and higher conductivity than those of the untreated solvent. The heats of mixing and electrical conductivity show a good correlation, underlining a single cause for the behaviour of the extremely diluted solutions.

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Abstract  

In this paper we try to perform a thermodynamic analysis of the temperature-induced transition from the molten globule to the unfolded state of globular proteins. A series of calorimetric investigations showed that this process is not associated with an excess heat capacity absorption peak, and cannot be regarded as a first-order phase transition. This result contrasts with the well-established conclusion that the thermal unfolding of the native tertiary structure of globular proteins is a first-order phase transition. First, the theoretical approach developed by Ikegami is outlined to emphasize that a second-order or gradual transition induced by temperature is expected for globular proteins when the various secondary structure elements do not interact cooperatively. Secondly, a simple thermodynamic model is presented which, taking into account the independence of the secondary structure elements among each other, is able to rationalize the shape of the experimental DSC profiles.

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Journal of Thermal Analysis and Calorimetry
Authors: Zhongliang Zhang, Fuming Liu, Manhong Liu, Zhenzhen Wang, Faping Zhong, and Feng Wu

Abstract  

Calorimetric measurements were carried out on the electrorefining of copper using different current densities with a Calvet type microcalorimeter at room temperature. The ratio (R) of the measured heat (Q m orW m) to the input electric energy (Q in orW in) and the excess heat (Q ex orW ex), i.e. the difference betweenQ m (orW m) andQ in (orW in) during the electrorefining process were discussed in terms of general thermodynamics. It was found thatR andQ ex were related to the current density employed in the experiment and varied as a logarithmic function. The results obtained here indicate that the heat generation under different conditions, such as different currents or voltages, may be caused partially by the irreversibility of the process or by some unknown processes.

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Abstract  

DSC was used for heat capacity measurements of pure RuO2 in the temperature range from 300 to 1170 K of solid solutions corresponding to the compositions of (Ti1−x Rux )O2 (x ≤0.15 and x ≥0.85) and in the temperature range from 300 to 1550 K of pure TiO2. The analysis of experimental data obtained within 2% of accuracy has shown that the characteristic temperatures representing the harmonic lattice vibrations do not strongly depend on the chemical composition x . It was demonstrated that non-harmonic heat capacity is strongly correlated to x. The existence of additional excess heat capacity was observed with the mixed oxide solid solution samples of low Ru content and explained by the defect formation model.

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Abstract  

New approaches to the analysis of differential scanning calorimetry (DSC) data relating to proteins undergoing irreversible thermal denaturation have been demonstrated. The experimental approaches include obtaining a set of DSC curves at various scanning rates and protein concentrations, and also reheating experiments. The mathematical methods of analysis include construction of a linear anamorphosis and simultaneous fitting of a theoretical expression for the dependence of the excess heat capacity on temperature to a set of experimental DSC curves. Different kinetic models are discussed: the one-step irreversible model, the model including two consecutive irreversible steps, the Lumry and Eyring model with a fast equilibrating first step, and the whole kinetic Lumry and Eyring model.

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Conductometric and calorimetric studies of the serially diluted and agitated solutions

On the combined anomalous effect of time and volume parameters

Journal of Thermal Analysis and Calorimetry
Authors: P. Belon, V. Elia, L. Elia, M. Montanino, E. Napoli, and M. Niccoli

Abstract  

We systematically analysed the experimental data related to the specific conductivities and heats in excess of several serially diluted and agitated solutions (SDA for short). For all of the analysed samples, we found that both the excess conductivity, χE (μS cm−1), and excess heat, Q mix E (J kg−1), varied with the age of the sample (up to 2 years of ageing). Furthermore, we found that after a certain period of ageing, small volume samples exhibited a much higher excess than large volume ones. The results we report in this paper are the product of a systematic study, during which we operated on known and constant volumes across the life of the samples. The incidence of volume on χE and Q mix E turned out to be overwhelming when compared with that of time. The temporal evolution of the smaller samples was found significantly higher than that of the larger volume ones. A careful numerical analysis of the results uncovered an extraordinary and unexpected correlation, of exponential kind, between the excess parameters and the volume of the solution in the container. As for the temporal evolution of these systems, we found that the measured excess heats and conductivity often reach a maximum. That led us to the conclusion that the temporal evolution of the physico-chemical parameters is not caused by the slow process of equilibrium attainment; on the contrary, these systems are far from equilibrium systems, dissipative structures, whose experimental behaviour is certainly due to the variation of the super-molecular structure of the solvent, water. The agitation phase during the preparation could be the trigger for the formation of dissipative structures and the emergence of the novel behaviour. We put forth a simple rationalizing hypothesis, based on the general idea of water as an auto-organizing system that, when elicited by even small perturbations, can enter a far from equilibrium state, sustained by the dissipation of the electromagnetic energy coming from the environment. (Dissipative Structures).

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Abstract  

An extensive study has been carried out on extremely diluted aqueous solutions (EDS). These solutions revealed a really intriguing physico-chemical behaviour, characterized by multiple independent variables. Because of their behaviour, EDS can be described as far-from-equilibrium systems, capable of self-organization as a consequence of little perturbations. In this paper we investigate the stability of the calorimetric behaviour of EDS with a high ionic force, due to the presence of the sodium chloride electrolyte. We measured the excess heats of mixing of EDS with basic solutions, both with and without a high concentration of NaCl, and compared the results. In particular, we explored these concentrations: 0.5 and 1Mmol kg−1). The analysis of the experimental results shows that the calorimetric response of the EDS is stable when they are in a concentrated solution of NaCl. That is of great relevance for the eventual pharmacological action of these solutions, since it involves the interaction with fluids of complex chemical composition and high concentration.

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Accurate determinations of excess heat capacities,C p E, of liquid and solid phases with respect to composition and temperature are shown to be possible by direct reaction calorimetry. The results are compared with those obtained by heat capacity measurements and departure from the additivity rule. In the case of solutions, the knowledge ofC p E with respect to concentration permits a pertinent analysis of the short-range order. Some results concerning binary alloys, such as In-Te, Cu-Sb and Ag-Te, are given.

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Abstract  

An extensive thermodynamic study has been carried out on aqueous solutions, obtained through the iteration of two processes: a dilution 1:100 in mass and a succussion. The iteration is repeated until extreme dilutions are reached (less than 1⋅10–5 mol kg–1 ) to the point that we may call the resulting solution an 'extremely diluted solution'. We conducted a calorimetric study, at 25C, of the interaction of those solutions with acids or bases. Namely, we measured the heats of mixing of acid or basic solutions with bidistilled water and compared them with the analogous heats of mixing obtained using the 'extremely diluted solutions'. Despite the extreme dilution of the latter solutions, we found a relevant exothermic excess heat of mixing, excess with respects to the corresponding heat of mixing with the untreated solvent. Such an excess has been found in about the totality of measurements, and of a magnitude being well beyond one that could arise any issue of sensibility of the instrumental apparatus. Here we thus show that successive dilutions and succussions can permanently alter the physico-chemical properties of the solvent water. The nature of the phenomena here described still remains unexplained, nevertheless some significant experimental results were obtained.

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