Thermodynamic Properties of Dimethylaminoarglabin Methyl Iodide C1 8H2 8O3NI and Its Analogs

The heat of solution of dimethylaminoarglabin methyl iodide C_{1 8}H_{2 8}O₃NI at dilutions (mole of salt/mole of water) of 1 : 75000, 1 : 100000, and 1 : 150000 was determined by isothermal calorimetry. The data obtained were used to calculate the standard heat of solution of the compound in an infinitely dilute (standard) aqueous solution. The heats of combustion, melting, and formation of C_{1 8}H_{2 8}O₃NI and 33 its analogs were estimated by approximate methods of chemical thermodynamics.     

Synthesis and X-ray diffraction and calorimetric studies of LaLiMnFeO5 and LaCsMnFeO5 ferrites

Ferrites LaLiMnFeO₅ and LaCsMnFeO₅ were synthesized for the first time by ceramic technology from mixtures of lanthanum(III), manganese, and iron(III) oxides with lithium or cesium carbonate. The compounds were shown by X-ray diffraction to crystallize in the orthorhombic system; the unit cell parameters were determined. The heat capacities were found experimentally for 298.15–673 K. Equations for the heat capacities as a function of temperature were derived and used to calculate the thermodynamic functions C _p ⁰ (T), S ⁰(T), H ⁰(T)?H ⁰(298.15), and Φ**(T) for the above temperature range.     

Ferrites YbSrFe2O5.5 and YbBaFe2O5.5: Synthesis and X-ray diffraction, thermodynamic, and electrophysical properties

Ferrites YbSrFe₂O_5.5 and YbBaFe₂O_5.5 are prepared by reacting ytterbium(III) oxide and iron(III) oxide with strontium or barium carbonate in the solid phase. The ferrites crystallize in the orthorhombic system as shown by indexing of their X-ray diffraction patterns with homology modeling: for YbSrFe₂O_5.5, a = 10.74 ± 0.006 Å, b = 10.93 ± 0.006 Å, c = 16.64 ± 0.046 Å, V ⁰ = 1953.3 ų, Z = 16, V _subcell ⁰ = 122.08 ų, ρ_X-ray = 6.26 g/cm³, ρ_pycn = 6.18 ± 0.9 g/cm³; for YbaBaFe₂O_5.5, a = 10.74 ± 0.013 Å, b = 10.99 ± 0.004 Å, c = 17.16 ± 0.017 Å, V ⁰ = 2025.4 ų, Z = 16, V _subcell ⁰ = 126.59 ų, ρ_X-ray = 6.69 g/cm³, ρ_pycn = 6.40 ± 0.32 g/cm³. The calorimetric heat capacities of the ferrites are studied from 298.15 to 673 K. The C _p ^o ～ f(T) curves show λ peaks at 448 K for YbSrFe₂O_5.5 and at 373 K for YbBaFe₂O_5.5, likely, due to second-order phase transitions. The dielectric constants and electrical resistances of the ferrites are studied as functions of temperature from 293 to 493 K.     

Synthesis and X-ray diffraction study of LaM 1.5 II MnFeO6 manganitoferrites (MII = Mg,Ca, Sr,Ba)

LaM _1.5 ^II MnFeO₆ manganitoferrites (M^II = Mg, Ca, Sr, Ba) have been synthesized by ceramic technology from lanthanum oxide, manganese(III) oxide, iron(III) oxide, and alkali-earth carbonates. X-ray powder diffraction shows that these compounds crystallize in cubic crystal system with the following unit cell parameters: for LaMg_1.5MnFeO₆: a = 20.232 ± 0.032 Å, V ⁰ = 8281.642 ± 0.096 ų, Z = 10, ρ_X = 7.38 g/cm³, ρ_pycn = 7.29 ± 0.06 g/cm³; for LaCa_1.5MnFeO₆: a = 20.056 ± 0.017 Å, V ₀ = 8067.388 ± 0.051 ų, Z = 8, ρ_X = 5.89 g/cm³, ρ_pycn = 5.78 ± 0.06 g/cm³; for LaSr_1.5MnFeO₆: a = 20.117 ± 0.021 Å, V ₀ = 8141.223 ± 0.063 ų, Z = 8, V _u.c. ⁰ = 1017.653 ± 0.008 ų, ρ_X = 6.64 g/cm³, ρ_pycn = 6.56 Å 0.08 g/cm³; for LaBa_1.5MnFeO₆: a = 20.361 ± 0.025 Å, V ₀ = 8441.066 ± 0.075 ų, Z = 8, ρ_X = 7.31 g/cm³, ρ_pycn = 7.25 ± 0.07 g/cm³.     

Heat capacity and thermodynamic functions of new nanostructured cuprate-manganite NdCa2CuMnO6

Heat capacities of nanostructured NdCa₂CuMnO₆ cuprate-manganite are measured by means of dynamic calorimetry on an IT-C-400 unit in the temperature interval of 298.15–673 K. It is established that a λ-shaped phase transition of the second kind is revealed at 348 K on the curve of the dependence C° _p ～ f(T) of NdCa₂CuMnO₆. Equations for the temperature dependence of the heat capacity of NdCa₂CuMnO₆ cuprate-manganite are derived from experimental data including the temperature of phase transition. Thermodynamic functions H°(T)-H°(298.15), S°(T), and Φ**(T) are calculated in the interval of 298.15–675 K.     

Thermochemistry of myricetin flavonoid

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 dissolution for the biologically active substance in an infinitely diluted (standard) solution of 96% ethanol are calculated from the experimental data. Physicochemical means of approximation are used to estimate the values of the standard enthalpy of combustion, and the enthalpy of melting is calculated for the investigated flavonoid. Finally, the compound’s standard enthalpy of formation is calculated using the Hess cycle.     

Chromites YbMCr<Subscript>2</Subscript>O<Subscript>5</Subscript> (M = Li,Na, K,Cs): X-ray diffraction study

Ytterbium alkali-metal chromites YbMCr₂O₅ (M = Li, Na, K, Cs) were synthesized by a ceramic procedure from the corresponding oxides and carbonates. Their crystal systems and unit cell parameters were determined by the homology method: for YbLiCr₂O₅, a = 10.34 Å, b = 10.62 Å, c = 15.05 Å, Z = 16, V ^o = 1653.74 ų, ρ_X-ray = 5.85 g/cm³, ρ_pycn = 5.81 ± 0.03 g/cm³; for YbNaCr₂O₅, a = 10.30 Å, b = 10.56 Å, c = 16.46 Å, Z = 16, V ^o = 1790.32 ų, ρ_X-ray = 5.64 g/cm³, ρ_pycn = 5.59 ± 0.07 g/cm³; for YbKCr₂O₅, a = 10.33 Å, b = 10.63 Å, c = 19.93 Å, Z = 16, V ^o = 2188.47 ų, ρ_X-ray = 5.95 g/cm³, ρ_pycn = 5.91 ± 0.03 g/cm³; and for YbCsCr₂O₅, a = 10.34 Å, b = 10.63 Å, c = 18.43 Å, Z = 16, V ^o = 2025.72 ų, ρ_X-ray = 5.19 g/cm³, ρ_pycn = 5.16 ± 0.05 g/cm³.     

Heat capacity and thermodynamic functions of new cobalt manganites NdM<Subscript>2</Subscript><Superscript>I</Superscript> CoMnO<Subscript>5</Subscript> (M<Superscript>I</Superscript> = Li,Na, and K) in the range of 298.15–673 K

Temperature dependences of the heat capacity of cobalt manganites NdM₂ ^I CoMnO₅ (M^I = Li, Na, and K) are studied by means of dynamic calorimetry in the range of 298.15?673 K. It is found that λ-shaped effects are observed on the C _p ^° ~ f (T) curve of cobalt manganites, due probably to second order phase transitions. Based on the experimental data, equations for the temperature dependences of the heat capacity of cobalt manganite are derived with allowance for the temperatures of phase transitions. The values of thermodynamic functions Н°(T)–Н°(298.15), S°(T), and Ф^хх(T) are calculated.     

Thermodynamics of a series of harmine alkaloid derivatives

The enthalpies of solution in water and ethanol of a series of harmine alkaloid derivatives, harminium di(o-carborano-1,2-dimethyl)borate, harminium tosylate, harminium thiocyanate, N(2)-hydroxyharminium hydrogen sulfate, and adduct of harmine N-oxide with phthalic anhydride, were determined by isothermal calorimetry. The standard heats of combustion, melting, and formation of these compounds were calculated by approximate methods.     

Synthesis and x-ray diffraction study of new nanostructured manganite ferrites NdM 1.5 II MnFeO6 (MII = Mg, Ca, Sr, Ba)

Manganite ferrites NdM _1.5 ^II MnFeO₆ (M^II = Mg, Ca, Sr, Ba) were synthesized from neodymium(III), manganese(III), and iron(III) oxides and alkaline-earth metal carbonates by a ceramic technology. By grinding the obtained compounds in a ball mill, their nanostructured particles were produced, the sizes of which were determined with an electron microscope. X-ray diffraction study established that the nanostructured compounds crystallize in the cubic and tetragonal systems with the following lattice parameters: NdMg_1.5MnFeO₆ (tetragonal): a = 10.955 Å, c = 17.848 Å, V ⁰ = 2141.975 ų, Z = 16, V _e1.cel1 ⁰ = 133.873 ų, ρ_X-ray = 4.80 g/cm³, and ρ_pycn = 4.76 ± 0.05 g/cm³; NdCa_1.5MnFeO₆ (cubic): a= 10.809 Å, V ⁰ = 1262.864 ų, Z = 8, V _e1.cel1 ⁰ = 157.858 ų, ρ_X-ray = 4.32 g/cm³, and ρ_pycn = 4.27 ± 0.03 g/cm³; NdSr_1.5MnFeO₆ (cubic): a = 10.911 Å, V ⁰ = 1298.953 ų, Z = 8, V _e1.cel1 ⁰ = 162.369 ų, ρ_X-ray = 4.93 g/cm³, and ρ_pycn= 4.88 ± 0.05 g/cm³; and NdBa_1.5MnFeO₆ (tetragonal): a = 11.011 Å, c = 18.001 Å, V ₀ = 2182.479 ų, Z = 16, V _e1.cel1 ⁰ = 136.405 ų, ρ_X-ray = 6.78 g/cm³, and ρ_pycn= 6.75 ± 0.07 g/cm³.