Titanium-manganites of LaLi₂TiMnO₆ and LaNa₂TiMnO₆ were synthesized by the methods of ceramic technology from the oxides of lanthanum, titanium (IV), manganese (III), and the carbonates of lithium and sodium. The types of their syngony and the parameters of their gratings were determined radiographically. The isobaric heat capacities of titanium-manganites were measured with experimental calorimetry in the range of 298.15–673 K. It was found that on the dependence curve of heat capacity versus temperature of C°_p~f(T), for LaLi₂TiMnO₆ at 348 K and 598 K, and LaNa₂TiMnO₆ at 348 K, there are abnormal jumps in heat capacity, probably related to phase transitions of the second kind. Taking into account the temperatures of the phase transitions, the equations of the temperature dependence of the heat capacity of titanium-manganites were derived. Their standard entropies were calculated by the ion increments method. Temperature dependences of the thermodynamic functions of S°(T), H°(T)-H°(298.15), and Φ^xx(T) were calculated using the experimental data on heat capacities and the calculated values of the standard entropies. The standard heat capacities of the studied compounds were calculated by the independent methods of ion increments and Debye, the values of which were in satisfactory agreement with the experimental data. The standard enthalpy of the formation of LaLi₂TiMnO₆ and LaNa₂TiMnO₆ was calculated according to the methodology developed by the authors. The conducted electrophysical studies determined the nature of the second-order phase transition and the semiconductor features of their conductivity. Thus, all the above-mentioned data on the experimental and calculated studies of the temperature dependence of heat capacity, the thermodynamic functions to determine a standard enthalpy of formation of LaLi₂TiMnO₆ and LaNa₂TiMnO₆, and the investigation of their electrical properties are absolutely new, and they have no analogues.

The method of isothermal calorimetry at dilutions (moles salt/moles water) of 1:9000, 1:18000, and 1:36000 was applied to study the heats of solution of methyl iodides of dimethyl-and diethylamino grosshemin. The data obtained were used to calculate the standard enthalpies of solution of C₁₈H₂₈O₄NI and C₂₀H₃₂O₄NI in an infinitely diluted (standard) aqueous solution. The heats of combustion and melting of C₁₈H₂₈O₄NI and C₂₀H₃₂O₄NI were estimated. The experimental and calculational techniques were combined to calculate the standard heats of formation of methyl iodides of dimethyl-and diethylamino grosshemin and their 66 analogues.

The enthalpies of myricetin dissolution are measured by means of calorimetry with mol dilutions of flavonoid: 96 mol % ethanol equal to 1: 9000, 1: 18000, and 1: 36000. The standard enthalpies of...

This paper studies the dependence of the specific heat capacity (C_p) of activated carbon obtained by the activation of coke fines on temperature (T, K) and the dependence of electrical resistance (R, Om) on temperature (T, K). In the course of the work, it was found that in the temperature range of 298.15–448 K on the curve of dependence C_p − f(T) at 323 K there is a jump in heat capacity, associated with a phase transition of the second kind. Measurements of the temperature dependence of electrical resistance on temperature were also carried out, which showed that activated carbon in the temperature range of 293–343 K exhibits metallic conductivity, turning into a semiconductor in the temperature range of 343–463 K. The calculation of the band gap showed that the resulting activated carbon is a semiconductor with a moderately narrow band gap. The satisfactory agreement of the phase transition temperatures on the curves of the temperature dependences of the heat capacity on temperature (323 K) and on the curves of the dependences of electrical resistance and the relative permittivity on temperature (343 K) indicates the nature of this phase transition, i.e., at a temperature of 323 K, the change in heat capacity is associated with the transition from semiconductor conductivity to metallic.

Temperature dependences of the heat capacities of cobalt manganites LaM2IICoMnO6 (MII= Mg, Ca, Sr, Ba) are investigated by means of dynamic calorimetry in the temperature range of 298.15–673 K. It...