Search Results
Abstract
The molar heat capacity, C p,m, of a complex of holmium chloride coordinated with L-aspartic acid, Ho(Asp)Cl2·6H2O, was measured from 80 to 397 K with an automated adiabatic calorimeter. The thermodynamic functions H T-H 298.15 and S T-S 298.15 were derived from 80 to 395 K with temperature interval of 5 K. The thermal stability of the complex was investigated by differential scanning calorimeter (DSC) and thermogravimetric (TG) technique, and the mechanism of thermal decomposing of the complex was determined based on the structure and the thermal analysis experiment.
Abstract
The thermodynamic functions for the extraction of Sc3+ by liquid cation exchangers HD and HDEHP are determined radiometrically by the temperature coefficient method. The role of diluent dielectric constant on the extraction of Sc3+ by HD is also studied. The thermodynamic parameters determined indicated that the free energy variation for the extraction of Sc3+ by HD is mainly determined by the entropic terms arising from the hydration—dehydration process of the exchanged ions. In the case of HDEHP as extractant, the free energy variations are determined mainly by the entalpic terms of the system.
Abstract
The results of recent developments on modelling of supramolecular ordering and physicochemical properties of molecular mixtures have been reviewed. The main attention is paid to the unified approach based on a generalized quasichemical model for a set of thermodynamic, dielectric and optical properties of mixtures, self-organized by specific bonding. Interrelations between thermodynamic, as well as dielectric, and optical properties of liquid mixtures, reflecting different molecular parameters, and the characteristics of quasichemical processes are presented. Applications for thermodynamic functions of mixing, permittivity, coefficients Rayleigh light scattering in molecular mixtures are considered. Data on thermodynamics of aggregation in mixtures have been obtained.
Abstract
The liquid-liquid extraction behavior of 2-ethylhexyltolylsulfoxide (EHTSO) towards uranium(VI) contained in nitric acid aqueous solution has been investigated. It was found that the extraction increases with increasing nitric acid concentration up to 5.0 mol/l and then decreases. Extraction also increases with increasing extractant concentration. The extracted species appears to be UO2(NO3)2 .2EHTSO. The influences of temperature, NH4NO3 and Na2C2O4 concentrations on the extraction equilibrium were also investigated and the thermodynamic functions of the extraction reaction were obtained.
Abstract
Phase diagrams of urea-α-naphthol and urea-benzoic acid systems, determined by the thaw-melt method, show the formation of simple eutectic in each case. The growth velocity data, determined at different undercooling (ΔT) by observing the rate of movement of interface in a capillary, obey the Hillig-Turnbull equation, v=u(ΔT)n, where u and n are constants depending on the nature of the materials. Using enthalpy of fusion, undercooling (ΔT) and melting point data, entropy of fusion, interfacial energy, enthalpy of mixing, critical radius size and excess thermodynamic functions were calculated. The microstructural investigations give characteristic features of the eutectics.
Abstract
The extraction behavior of octahedral and tetrahedral cobalt(II) complexes from aqueous nitrate medium was studied in the system 8-hydroxyquinoline (HOX) and dibenzo-18-crown-6 (Db 18C6) or dibenzylamine (DBA) in chloroform at different temperatures to evaluate the thermodynamic functions as well as the equilibrium constants of each reaction. The stoichiometry of the extracted organic phase species were established to be Co(OX)2·Db18C6 for the octahedral cobalt and Co(OX)2·DBA for the tetrahedral cobalt.
Abstract
A new extractant, N-octanoyl-2-methylpiperidine (OMPPD) has been synthesized. The extraction of U(VI) with N-octanoyl-2-methylpiperidine (OMPPD) in nitric acid has been studied. The dependence of the partition reaction of U(VI) on the concentrations of nitric acid, extractant, salting-out agent LiNO3, and temperature has been studied. In the light of the results, the extraction mechanism is discussed. The synergistic extracted complexes may be presented as UO2(NO3)2(OMPPD)2 . The related thermodynamic functions were calculated.
Abstract
The liquid-liquid extraction behavior of octyldodecylsulfoxide (ODoSO) towards uranium(VI), contained in nitric acid aqueous solution, has been investigated. It was found that the extraction increased with increasing nitric acid concentration up to 2.0 mol/l and then decreased. Extraction also increases with increasing extractant concentration. The extracted species appears to be UO2(NO3)2 .2ODoSO. The influences of temperature, sodium nitrate and oxalate concentrations on the extraction were also investigated and the thermodynamic functions of the extraction reaction were obtained.
Abstract
Heat capacity of stoichiometric homogeneous spinel MgFe2O4 was measured from 5 to 305 K and thermodynamic functions were derived for temperatures up to 725 K using our previous high-temperature experimental data for the same sample. Anomaly in C p was found at very low temperatures. Experimental data below 20 K contain large (up to 25% near 5 K) error arising from the difference in the thermal history between the experimental series. Magnetic contribution to the low-temperature heat capacity was tested, and the linear function was found to fit experimental data better than the three-halves power derived from the spin-wave theory.
Abstract
Synthetic enstatite MgSiO3 was crystallized from a melt, quenched into water, and then annealed at 873 K. The product is the monoclinic polymorph with the unit cell parameters of a=0.9619(7), b=0.8832(3), c=0.5177(4) nm, β=108.27(5)°. Heat capacity was measured from 6 to 305 K using an adiabatic vacuum calorimeter. Thermodynamic functions for clinoenstatite differ by about 5% from those predicted after a thermodynamic model in the literature, but are very close to those measured for orthorhombic enstatite.
