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1.
Calcium–cadmium chlorapatites solid solutions with the general formula Ca10–xCdx(PO4)6Cl2,1≤x≤10, were prepared by solid state reaction and characterized by X-ray diffraction, infrared spectroscopy and chemical analysis.
Using an isoperibol calorimeter, their enthalpies of solution in 9 mass% nitric acid were measured. In order to determine
the enthalpies of formation and enthalpies of mixing, thermochemical cycles were proposed and complementary experiences were
performed. The results obtained show a decrease of the enthalpy of formation with the amount of cadmium introduced in the
lattice. The variation of mixing enthalpy vs. x=Cd/(Cd+Ca) shows a maximum at about x=0,4. This could be explained by the existence of two cationic sites in the phosphoapatite structure.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
Sonia Jebri Habib Boughzala Ali Bechrifa Mohamed Jemal 《Journal of Thermal Analysis and Calorimetry》2012,107(3):963-972
“A” type phosphostrontium carbonate hydroxyapatites, having the general formula Sr10(PO4)6(OH)(2−2x)(CO3)
x
with 0 ≤ x ≤ 1, were synthesised by solid gas reaction at high temperature. The samples were characterised by X-ray diffraction and
infrared spectroscopy. Analysis of carbonate was achieved by coulometry and Rietveld refinement of the structure. Using an
isoperibol calorimeter, the heat of solution of these products was measured at 298 K in 9 wt% nitric acid solution. Thermochemical
cycle was proposed and complementary experiences were performed to reach the standard enthalpies of formation of these compounds.
The results showed a decrease of the enthalpy of formation with the amount of carbonate introduced in the lattice, suggesting
an increase of stability due to this kind of substitution. 相似文献
3.
P. V. Verdes M. M. Mato J. L. Legido E. Jiménez M. I. Paz Andrade 《Journal of Thermal Analysis and Calorimetry》2007,88(2):613-616
Excess molar enthalpies
of the ternary system {x
1
p-xylene+x
2decane+(1–x
1–x
2)diethyl
carbonate} and the involved binary mixtures {p-xylene+(1–x)decane}, {xp-xylene+(1–x)diethyl carbonate} and {xdecane+(1–x)diethyl carbonate} have been determined at the
temperature of 298.15 K and atmospheric pressure, over the whole composition
range, using a Calvet microcalorimeter. The experimental excess molar enthalpies H
m
E
are positive for all the binary systems studied over the whole composition
range. Excess molar enthalpy for the ternary system is positive as well, showing
maximum values at x
1=0, x
2=0.4920, x
3=0.5080, H
m,123
E=1524
J mol–1. 相似文献
4.
K. I. Shatalov S. N. Solov’ev 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(2):331-333
The enthalpies of interactions of (NO2)2[NiF6](cr) with water and aqueous KOH, enthalpies of solution of KF(cr) in dilute aqueous solutions of KNO3 and KOH, and enthalpy of mixing of solutions of NiF2, HNO3, and HF were measured at 298.15 K using isothermic-shell calorimeters. Based on the obtained data and values in the literature,
the standard enthalpy of formation of the compound under study was determined by two independent methods: Δf
H°(NO2)2[NiF6](cr) = −1099 ± 9 kJ/mol. 相似文献
5.
V. G. Badelin V. I. Smirnov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(7):1163-1168
The integral enthalpies of solution of L-methionine in water-methanol, water-ethanol, water-n-propanol, and water-iso-propanol mixtures were measured calorimetrically at alcohol concentrations x
2 = 0–0.4 mole fractions. The standard enthalpies of solution (Δsol
H
o) and transfer of L-methionine (Δtr
H
o) from water to a binary solvent were calculated. The influence of the structure and properties of L-methionine and the composition
of aqueous-organic mixtures on its enthalpy characteristics was considered. The enthalpic pair interaction coefficients (h
xy
) between L-methionine and alcohol molecules were calculated; they were positive and increased in the series methanol (MeOH),
ethanol (EtOH), n-propanol (n-PrOH), iso-propanol (i-PrOH). The enthalpy characteristics of solution and transfer of L-methionine were compared with those of glycine, L-threonine,
L-alanine, and L-valine in similar binary solvents. 相似文献
6.
Yu. G. Shvedenkov V. N. Ikorskii L. G. Lavrenova V. A. Drebushchak N. G. Yudina 《Journal of Structural Chemistry》1997,38(4):578-584
The effect of Fe2+ substitution by Ni2+ in the complex of iron(II) nitrate with 4- amino- 1,2,4- triazole Fe(ATr)3(NO3)2 on the character of the1A1
5T2 spin transition (ST) is studied by magnetic susceptibility and calorimetry methods. Solid phases of FexNi1- x(ATr)3(NO3)2 (0.1 ≤ x ≤ 0.9) were synthesized. The temperature dependences of the effective magnetic moment were measured in the range
of 78– 360 K. Heat capacities were measured in the range of 210– 340 K for 0.1 ≤ x ≤ 0.5 and in the range of 230– 340 K
for 0.6 ≤x ≤ 0.9. As x decreases, the transition temperature (TC), hysteresis (δTC, and transition enthalpy (δH) decrease and the ST is leveled. The results are compared with the data obtained previously
for the solid phases of FexZn1- x(ATr)3(NO3)2 (0.01 ≤ x ≤ 0.8). The dependence Μeff(T) is analyzed theoretically in terms of both the domain model and the spin equilibrium model.
Translated fromZhumal Strukturnoi Khimii, Vol. 38, No. 4, pp. 696–703, July–August, 1997. 相似文献
7.
M. I. Ivanov V. V. Berezutskii V. G. Kudin M. A. Shevchenko V. S. Sudavtsova 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(12):2068-2073
Partial and integral enthalpies of mixing of melts of the Eu-Pd system were determined by calorimetry at 1300 K in the concentration
interval of 0 < x
Pd < 0.37. It was established that the first partial enthalpy of mixing of Pd was −158 ± 2 kJ/mol. The thermodynamic properties
of Eu-Pd melts were simulated according to the theory of ideal associated solutions over a wide interval of concentrations
and temperatures. It was shown that the activities of components display strong negative deviations from Raoult’s law, and
the minima of the integral Gibbs energies and enthalpies of mixing were found at x
Pd = 0.65. 相似文献
8.
M. V. Kulikov 《Russian Chemical Bulletin》1997,46(2):274-278
The enthalpies of mixing of acetonitrile with formamide,N-methylformamide,N,N-dimethylformamide, and hexamethylphosphoric triamide were measured in the temperature interval from 283.15 to 328.15 K. The
enthalpy coefficients of binary and ternary interactions were calculated by the methods of the McMillan-Mayer theory. The
contributions to the enthalpy of solution due to the formation of a cavity in the solvent, Δcav
H°, and those due to the interaction of the solute with the solvent, Δint
H°, were determined. The enthalpies of the specific and non-specific solvation of acetonitrile in the corresponding amides
were calculated. Specific interactions were found to contribute the most to the solvation enthalpy of acetonitrile. The obtained
values were compared with analogous values for solutions of acetonitrile in water and alcohols.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 289–293, February, 1997. 相似文献
9.
A. S. Monaenkova A. A. Popova L. A. Tiflova E. A. Gudilin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(8):1280-1284
The enthalpies of reactions of substitution solid solutions Pr1 + x
Ba2 − xCu3O
y
, where x = 0, 0.2, 0.4, 0.6, and 0.9, with 1.07 N HCl were measured at 298.15 K in a hermetic swinging isothermic-shell calorimeter.
The results and the literature data were used to calculate the standard enthalpies of formation of solid solutions from the
elements and oxides. The dependence of the enthalpy of solid solution formation on the degree of praseodymium substitution
for barium (x) was revealed. 相似文献
10.
V. S. Sudavtsova N. V. Kotova V. G. Kudin L. A. Romanova T. N. Zinevich 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(2):176-179
The partial mixing enthalpies of the components (Δm
$
\bar H
$
\bar H
i
) of the Ni-Ga melts were measured using the high-temperature isoperibolic calorimetry at 1770 ± 5 K in wide concentration
interval. The limiting partial mixing enthalpy of gallium in a liquid nickel (Δm
$
\bar H
$
\bar H
Ga∞) is −95.5 ± 19.8 kJ mol−1, and similar function of nickel in liquid gallium (Δm
$
\bar H
$
\bar H
Ni∞) is −74.5 ± 16.4 kJ mol−1. The integral mixing enthalpy of liquid alloys of this system was calculated from partial enthalpies for the whole concentration
area (Δm
H
min = −32.1 ± 2.7 kJ mol−1 at x
Ni = 0.5). The Δm
H value of liquid nickel-gallium alloys independence of the temperature is confirmed. Enthalpies of formation of liquid (Δm
H) phases of Ni-Ga system were compared with ones for solid (Δf
H) phases of this system. An analysis of d-metals influence on formation energy of Ga-d-Me melts was made using the values of Δf
H for intermediate phases of these systems. The article was translated by the authors. 相似文献
11.
L. F. Brum Malta Marta Eloisa Medeiros 《Journal of Thermal Analysis and Calorimetry》2007,87(3):883-886
This work reports the study of Bi4V2–xBaxO11–1.5x (0.02≤x≤0.50)
series, which is a potential source of solid electrolytes to apply in oxygen
sensors. X-ray powder diffraction was used to point out the formation of major
ionic conductive phases and minor ones. The modifications of vanadate substructure
were probed, at short range, by Fourier-transform infrared spectroscopy. Differential
scanning calorimetry evidenced the formation of tetragonal γ phase, which
can be ionic conductive, for x=0.14. 相似文献
12.
The enthalpy of mixing of formamide,N-methylformamide,N,N-dimethylformamide, and hexamethylphosphoric triamide with MeCN was measured in the 283–328 K range. The enthalpic coefficients
of the binary and ternary interactions between the amide molecules are calculated within the framework of the McMillan-Mayer
theory. The contributions to the enthalpy of dissolution due to cavity formation in the solvent (Δcav
H
0) and due to solute-solvent interaction (Δint
H
0) were determined. The enthalpies of specific and nonspecific solvation of amides in MeCN were calculated. The main contribution
to the enthalpy of solvation of formamide andN-methylformamide is from specific interactions, while forN,N-dimethylformamide and hexamethylphosphoric triamide it is from nonspecific interactions. The values obtained are compared
with those for solutions of the amides mentioned in water and methanol.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1730–1735, October, 1993. 相似文献
13.
V. G. Badelin V. I. Smirnov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(6):944-947
Solution enthalpies of DL-α-alanyl-DL-α-asparagine (AlaAsn) in water-formamide, water-N-methylformamide, water-N,N-dimethylformamide, and water-N,N-dimethylacetamide mixtures were measured in the range of amide mole fractions x
2 = 0–0.3. The standard enthalpies of solution (Δsol
H°) and transfer (Δtr
H°) of AlaAsn from water to the binary solvent and enthalpy coefficients of pair-wise interactions (h
xy
) of AlaAsn with amide molecules were calculated. The influence of the composition of the water-organic mixture on the enthalpy
characteristics of AlaAsn is discussed. It is shown that the enthalpy characteristics of solution and transfer of AlaAsn are
related to the structure of amides. 相似文献
14.
S. N. Solov’yov A. A. Firer A. Ya. Dupal 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(4):689-691
The enthalpies of interaction of (XeF5)2[MnF6](cr) with a 0.0524 m solution of KOH and a 0.0300 m solution of H2SO4, the enthalpy of solution of KMnO4(cr) in a 0.0440 m solution of KOH, and the enthalpy of mixing of aqueous KF with alkaline KMnO4 were measured in isothermic-shell calorimeters at 298.15 K. The standard enthalpy of formation of the compound at 298.15
K was calculated by two independent procedures using the experimental values and literature data (Δf
H
o = −1185 ± 18 kJ/mol).
Original Russian Text ? S.N. Solov’yov, A.A. Firer, A.Ya. Dupal, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol.
83, No. 4, pp. 798–800. 相似文献
15.
Sophie Guillemet-Fritsch Philippe Tailhades Miaojun Wang 《Journal of solid state chemistry》2005,178(1):106-113
Oxide melt solution calorimetry has been performed on iron manganese oxide spinels prepared at high temperature. The enthalpy of formation of (MnxFe1−x)3O4 at 298 K from the oxides, tetragonal Mn3O4 (hausmannite) and cubic Fe3O4 (magnetite), is negative from x=0 to x=0.67 and becomes slightly positive for 0.67<x<1.0. Relative to cubic Mn3O4 (stable at high temperature) and cubic Fe3O4 (magnetite), the enthalpy of formation is negative for all compositions. The enthalpy of formation is most negative near x=0.2. There is no significant difference in the trend of enthalpy of formation versus composition for cubic (x<0.6) and tetragonal (x>0.6) spinels of intermediate compositions. The enthalpies of formation are discussed in terms of three factors: oxidation-reduction relative to the end-members, cation distribution, and tetragonality. A combination of measured enthalpies and Gibbs free energies of formation in the literature provides entropies of mixing. ΔSmix, consistent with a cation distribution in which all trivalent manganese is octahedral and all other ions are randomly distributed for x>0.5, but the entropy of mixing appears to be smaller than these predicted values for x<0.4. 相似文献
16.
L. A. Dreval’ A. R. Abdulov P. G. Agraval M. A. Turchanin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(7):1118-1121
The partial enthalpy of mixing of vanadium in three-component Cu-Fe-V melts was studied at 1873 K along sections with constant
x
Cu/x
Fe ratios of 3, 1, and 1/3 over the composition range x
V = 0–0.55 by high-temperature isoperibolic calorimetry. The Muggianu-Redlich-Kister model was used to describe the concentration
dependence of the integral enthalpy of mixing of Cu-Fe-V melts over the whole concentration triangle. The contribution of
ternary interaction to the integral enthalpy of mixing of Cu-Fe-V melts was calculated. 相似文献
17.
Typical
data of a new microporous material obtained from gels with titanium and silicon 总被引:1,自引:0,他引:1
M. Veltri D. Vuono P. De
Luca J. B. Nagy A. Nastro 《Journal of Thermal Analysis and Calorimetry》2006,84(1):247-252
The
aim of this work is the synthesis and the characterization of a microporous
material obtained from gels with titanium and silicon: NTS (titanosilicate).
The structure of NTS zeotype is similar to that of AM-1 and JDF-L1 (titanosilicates).
The synthesis were carried out with gels
of composition: 3.5Na2O–yTiO2–4.48HCl–xSiO2–110H2O
with 1.0≤x≤12.0 and 0.2≤y≤0.7. The temperature of reaction was 190±2°C. 相似文献
18.
Thermal behavior of xGa2O3–(50 − x)PbO–50P2O5 (x = 0, 10, 20, and 30 mol.% Ga2O3) and xGa2O3–(70 − x)PbO–30P2O5 (x = 0, 10, 20, 30, and 40 mol.% Ga2O3) glassy materials were studied by thermo-mechanical analysis (TMA) and differential thermal analysis (DTA). Replacement of
PbO for Ga2O3 is accompanied by increasing glass-transition temperature (263 ≤ T
g/°C ≤ 535), deformation temperature (363 ≤ T
d/°C ≤ 672), crystallization temperature (396 ≤ T
c/°C ≤ 640) and decreasing of coefficient of thermal expansion (5.1 ≤ CTE/ppm K−1 ≤ 16.7). Values of Hruby parameter were determined (0.1 ≤ K
H ≤ 1.3). The thermal stability of prepared glasses increases with increasing of concentration of Ga2O3. 相似文献
19.
M. M. Mato M. Illobre P. V. Verdes J. L. Legido E. Jiménez M. I. Paz Andrade 《Journal of Thermal Analysis and Calorimetry》2007,88(2):607-611
Excess molar enthalpies
of the ternary mixture {x
1
tert-butyl methyl ether (MTBE)+x
2
ethanol+(1–x
1–x
2) octane} and the involved
binary mixture {x ethanol+(1–x) octane} have been measured at 298.15 K and atmospheric
pressure, over the whole composition range, using a Calvet microcalorimeter.
The results were fitted by means of different variable degree polynomials. 相似文献
20.
P. V. Verdes M. M. Mato J. L. Legido E. Jiménez M. I. Paz Andrade 《Journal of Thermal Analysis and Calorimetry》2007,88(2):583-586
Excess molar enthalpies, H
E,
for the binary mixtures {p-xylene+(1–x) octane}, {x
p-xylene+(1–x)
diethyl carbonate}, {x octane+(1–x) diethyl carbonate} and the corresponding ternary
system {x
1
p-xylene+x
2
octane+(1–x
1–x
2) diethyl carbonate} have
been measured by using a Calvet microcalorimeter at 298.15 K under atmospheric
pressure. The experimental H
E
values are all positive for the binary and ternary mixtures over the entire
composition range. 相似文献