Calorimetric Research into the Heat Capacity of Novel Nano-Sized Cobalt(Nickelite)-Cuprate-Manganites of LaBaMeIICuMnO6 (MeII = Co, Ni) and their Thermodynamic Properties

The isobaric heat capacities of novel nano-sized cobalt-cuprate-manganite of lanthanum and barium LaBaCoCuMnO6 and nickel-cuprate-manganite of lanthanum and barium LaBaNiCuMnO6 were investigated by dynamic calorimetry over the temperature range of 298.15‒673 K. It is found that a λ-shaped effect is observed on the curve of the heat capacity dependence on temperature of LaBaCoCuMnO6 at 523 K, while LaBaNiCuMnO6 also has a similar effect at 473 K. Equations for the temperature dependence of the heat capacity of cobalt(nickelite)-cuprate-manganite of lanthanum and barium are derived with allowance for the temperatures of phase transitions. Based on the experimental data, the fundamental constants ‒ the standard heat capacities of the compounds under study were found. Irrespective of the experimental data, we also calculated the standard heat capacities of the mentioned compounds using the Debye theory using the characteristic temperatures of the elements, their melting points, the Koref and Nernst-Lindemann equations. The obtained calculated data on C0p (298.15) of the compounds were in satisfactory agreement with the experimental data on the standard heat capacity. The standard entropies of LaBaCoCuMnO6 and LaBaNiCuMnO6 were calculated by the ion increment method. We calculated the temperature dependences of the enthalpy Ho(T)- Ho(298.15), entropy ΔSo(T), and the reduced thermodynamic potential ΔФ**(Т).

A study of the electrolytic solution process using the scaled particle theory. 5. Heat capacity of aqueous ions at elevated temperatures

A theory composite of the scaled particle theory and the Born model of solvent continuum has been used to theoretically calculate the standard heat capacity of hydration as well as the partial molal heat capacity of aqueous ions and electrolytes at elevated temperatures. The uncertainties in the second temperature derivatives of solvent dielectric constant at various temperatures present a barrier to an accurate heat capacity prediction by the theory. Nevertheless, the agreement between the predicted standard heat capacity of electrolytes in solution and the corresponding experimental data, particularly at higher temperatures, is encouraging. Moreover, the composite theory seems to provide the most accurate thermodynamic predictions to date for aqueous electrolytes at higher temperatures without involving any arbitrary adjustable parameter. We therefore use this theory to find the proper ionic scale of the partial molal heat capacities at elevated temperatures. Key words: scaled particle theory, solvent continuum model of Born, standard heat capacity of aqueous ions, absolute scale for hydration thermodynamic quantities.