Enthalpy

Experimental studies of the multicomponent systems are necessary in the development of new materials which can be used in various industries. The literature review showed, that the liquid phase in the silver–gallium–indium system has not been studied yet. In the present work the heat of mixing of the liquid silver–indium and silver–gallium–indium alloys was studied using Calvet type MHTC96 calorimeter. Calorimetric measurements were carried out at the temperatures: 973 K, 1123 K and 1273 K for Ag–In alloys, and at 923 K, 1123 K and 1273 K along two cross-sections XAg/XGa = 1:1 and XGa/XIn = 1:1 for Ag–Ga–In alloys. Next, the Redlich–Kister–Muggianu formalism was applied in the mathematical description of the heat of mixing of the liquid silver–gallium–indium alloys. Experimental results obtained in this work are first, which provided information about the thermodynamic properties of the liquid phase in this ternary system.

The role of water in bovine milk is more complicated than that of a background solvent. To understand the interaction between water and the constituents of milk, an extensive dielectric study of the γ-dispersion of raw bovine milk was carried out over the frequency range 0.1-50GHz and the interval of temperatures (10°C-42°C). Samples were provided by utilizing an extended donor pool. The results reveal that the temperature dependence of the characteristic relaxation times is described by the Arrhenius law. Furthermore, it conforms to a Meyer-Neldel compensation, whereby the pre-factor of the relaxation times is dependent on the activation energy. This entropy/enthalpy compensation is traced to the interaction between bulk water dynamic clusters and other milk constituents. A statistical correlation between the Somatic Cell Count, a traditional measure of milk quality, and the relaxation times is provided as well, opening new vistas for the industrial classification of milk.

The role of water in bovine milk is more complicated than that of a background solvent. To understand the interaction between water and the constituents of milk, an extensive dielectric study of the γ-dispersion of raw bovine milk was carried out over the frequency range 0.1-50GHz and the interval of temperatures (10°C-42°C). Samples were provided by utilizing an extended donor pool. The results reveal that the temperature dependence of the characteristic relaxation times is described by the Arrhenius law. Furthermore, it conforms to a Meyer-Neldel compensation, whereby the pre-factor of the relaxation times is dependent on the activation energy. This entropy/enthalpy compensation is traced to the interaction between bulk water dynamic clusters and other milk constituents. A statistical correlation between the Somatic Cell Count, a traditional measure of milk quality, and the relaxation times is provided as well, opening new vistas for the industrial classification of milk.

The dependence of the enthalpy change of formation of saturated acyclic ketones on molecular structure (the number of carbon atoms, the position of the carbonyl group, and the branching of the molecules) was investigated. For this purpose, a simple computational model, the parameterization of which is based on spectral graph theory, was developed. It was found that the major part of the enthalpy change of formation is determined by molecular size, whereas the fine structure of the enthalpy change of formation is determined by the branching of the molecule and the position of the carbonyl group. The developed model proved itself very useful for such investigations. The model is simple and practical, and the agreement between the experimental and calculated enthalpy changes of formation is very good, with an average relative error of 0.7%.

In our previous work on this topic, the Lennard-Jones potential was used to derive a semi-empirical formula relating the enthalpy of vaporization of a liquid to the density of the liquid and vapour at equilibrium with it, and a very good agreement between the formula and experimental data was demonstrated. In the present work, this approach has been further developed. The purpose of this work was to apply the Lennard-Jones potential to derive a semi-empirical formula describing the dependence of the surface tension of a liquid on temperature, as well as the dependence of the formation enthalpy of a binary solution on its composition. Solution formation was considered as consisting of two stages: 1) removal of x moles of the first component and 1– x moles of the second component from pure liquids into vacuum; in this case, the expended energy is equal to the energy of interaction of these molecules with all molecules in the volume of these liquids in accordance with the Lennard-Jones...

A new medium, eggshell powder has been developed for fluoride removal from aqueous solution. Fluoride adsorption was studied in a batch system where adsorption was found to be pH dependent with maximum removal efficiency at 6.0. The experimental data was more satisfactorily fitted with Langmuir isotherm model. The kinetics and the factor controlling adsorption process fully accepted by pseudo-second-order model were also discussed. Eawas found to be 45.98 kJmol-1by using Arrhenius equation, indicating chemisorption nature of fluoride onto eggshell powder. Thermodynamic study showed spontaneous nature and feasibility of the adsorption process with negative enthalpy (∆H0) value also supported the exothermic nature. Batch experiments were performed to study the applicability of the adsorbent by using fluoride contaminated water collected from affected areas. These results indicate that eggshell powder can be used as an effective, low-cost adsorbent to remove fluoride from aqueous solut...

The thermal denaturation of bovine serum albumin (BSA) is a kinetically and thermodynamically controlled process. The effects of zinc binding to bovine serum albumin (BSA), followed by differential scanning calorimetry (DSC), were investigated in this work, with the purpose of obtaining a better understanding of the albumin/zinc interaction. From the DSC curves, the thermodynamic parameters of protein denaturation were obtained, i.e., the temperature of thermal transition maximum (T m), calorimetric enthalpy (?Hcal), van't Hoff enthalpy (?HvH), the number of binding sites (I, II), the binding constants for each binding site (K bI, K bII) and the average number of ligands bound per mole of native protein X N. The thermodynamic data of protein unfolding showed that zinc binding to bovine serum albumin increases the stability of the protein (higher values of ?Hcal) and the different ratio ?Hcal/?HvH indicates the perturbation of the protein during thermal denaturation.

A new formulation for extending the concept of heatlines and masslines to reacting flows through use of conserved scalars has been proposed. The formulation takes into account the distinct diffusion coefficients of different species. Results have been obtained for a number of two-dimensional nonreacting and reacting free shear flows under normal and zero gravity. For nonreacting flows, total enthalpy and elemental mass fractions have been used as the transported conserved scalars. For reacting flows, mixture fractions, defined as normalized elemental mass fractions and enthalpy, have been employed. The results show this concept to be a useful tool for obtaining better insights into the global qualitative picture of scalar transport for both nonreacting and reacting flows.

The correct mathematical description of heat capacities Cp in a wide range of temperatures is still unsolved problem. A fragmental description of some phases is like a vision of one part of a large mosaic picture. A single description of Cp or other property of a phase of any isostructural series does not allow one to see the integrity of the entire ensemble. We propose a special mathematical model to describe Cp in a wide temperature range for a whole large class of isostructural sphalerite phases. In the proposed model, it is believed that an ideal crystal does
not have any foreign inclusions, defects, or dislocations. The group IV elements (Si, Ge, α-Sn and diamond-like Pb) were taken as the basis, with flerovium (114Fl) closing this group. There should be no other elements in this group according to the fine structure constant (α) (or the Sommerfeld constant). As a consequence, the limiting value of the heat capacities of phases with a sphalerite structure falls on the element 114 (114Fl) and has a value of Cp = 30.5 ± 0.3 J ⋅ mol-at􀀀 1 ⋅ K􀀀 1. This value was obtained as a maximal virtual point Cp of the last element (114Fl) of group IV and corresponds to Ln (Cp/R) = 1.30 ± 0.01 for the isotherms ln (Cp/R) vs Ln(N), where N is an atomic number of an element of group IV or the sum of the atomic numbers of AIIIBV or AIIBVI compounds per
mole-atom. The common point of heat capacity attributable to flerovium is obtained from the linear equations Ср/R vs Ln(N) at low temperatures from 25 to 35K. For only pure elements of group IV (Si, Ge, α-Sn and
diamond-like Pb), flerovium closes this group, and there are no other elements behind it, according to α. The maximum heat capacity of flerovium can be taken as 30.5 J⋅mol-at􀀀 1⋅K􀀀 1 with an accuracy of 1%. As the temperature decreases, this value slowly decreases (within 1%), and then, when it approaches 0 K, it drops sharply to 0 J⋅mol-at􀀀 1⋅K􀀀 1. To describe the set of the isostructural experimental data Cp(T) for diamond-like phases in solid state as a whole system, here we used a special multi-parameter family of functions. For each substance, the parameters are found by minimizing the discrepancy between the theoretical dependence Cp(T) and corresponding experimental data. The dependence of the heat capacities for elements of group IV (Si, Ge,
α-Sn, diamond-like Pb, Fl) at fixed temperatures on Ln(N), where N is the atomic number or the demi sum of the atomic numbers of phases AIIBVI or AIIIBV. In this case, either a break point or an inflection point attributable to germanium is observed for parameter dependencies on Ln(N).

An isoconversional method is proposed to be used for evaluating activation energy of protein denaturation. Applied to DSC data on collagen denaturation, the method yields an activation energy that decreases throughout the process. The Lumry‐Eyring model gives an explanation for this decrease and affords estimates for the enthalpy of the reversible step and the activation energy of the irreversible step of denaturation. The reversible unfolding is detectable by multi‐frequency temperature‐modulated DSC.magnified image

Based on unsteady state heat conduction, a mathematical model has been developed to describe the simultaneous heat and moisture transfer during potato frying. For the first time, the equation was solved using both enthalpy and Variable Space Network (VSN) methods, based on a moving interface defined by the boiling temperature of water in a potato disc during frying. Two separate regions of the potato disc namely fried (crust) and unfried (core), were considered as heat transfer domains. A variable boiling temperature of the water in potato discs was required as an input parameter for the model as the water is evaporated during frying, resulting in an increase in the soluble solid concentration of the potato sample. Pulsed electric field (PEF) pretreatment prior to frying had no significant effect on the measured moisture content, thermal conductivity or frying time compared to potatoes that did not receive a PEF pretreatment. However, a PEF pretreatment at 1.1 kV/cm and 56 kJ/kg red...