[Sm（C7H5O3）2（C4H6NO2S）]·2H2O was synthesized from the reaction of samarium chloride hexahydrate with salicylic acid and thioproline,and characterized by IR,elemental analysis and thermogravimatric analysis.Th...[Sm（C7H5O3）2（C4H6NO2S）]·2H2O was synthesized from the reaction of samarium chloride hexahydrate with salicylic acid and thioproline,and characterized by IR,elemental analysis and thermogravimatric analysis.The standard molar enthalpies of the solutions of SmCl3·6H2O（s）,2[C7H6O3（s）],[C4H7NO2S（s）] and [Sm（C7H5O3）2·（C4H6NO2S）·2H2O（s）] in a mixed solvent of absolute ethyl alcohol,dimethyl formamide（DMF） and 3 mol/L HCl were,respectively,determined by calorimetry to be ΔsHm^Θ [SmCl3·6H2O（s）,298.15 K]=（-46.68±0.15） kJ/mol,ΔsHm^Θ [2C7H6O3（s）,298.15 K]=（25.19±0.02） kJ/mol,ΔsHm^Θ [C4H7NO2S（s）,298.15 K]=（16.20±0.17） kJ/mol and ΔsHm^Θ {[Sm（C7H5O3）2（C4H6NO2S）]·2H2O（s）,298.15 K}=（-81.24±0.67） kJ/mol.The enthalpy change of the reaction SmCl3·6H2O（s）＋2C7H6O3（s）＋C4H7NO2S（s）=[Sm（C7H5O3）2（C4H6NO2S）]·2H2O（s）＋3HCl（g）＋4H2O（l） was determined to be ΔrHm^Θ =（123.45±0.71） kJ/mol.From the data in the literature,the standard molar formation enthalpy of [Sm（C7H5O3）2（C4H6NO2S）]·2H2O（s） was estimated to be Δf Hm^Θ {[Sm（C7H5O3）2（C4H6NO2S）]·2H2O（s）,298.15 K}=（-2912.03±3.1） kJ/mol through Hess＇ law.展开更多
The relationship between temperature and oxygen vacancy concentration is deduced in this paper. Based on the data of thermal weight-loss experiment, the formation enthalpies of congruent and several doped LN crystals ...The relationship between temperature and oxygen vacancy concentration is deduced in this paper. Based on the data of thermal weight-loss experiment, the formation enthalpies of congruent and several doped LN crystals have been calculated. It was found that the formation enthalpy of oxygen vacancies can be decreased evidently by doping valence-changeable ions. The experimental results were discussed and a new reduction process of the photorefractive LN crystal at a relatively low temperature was proposed, and the reduced crystals showed a good effect in practical use.展开更多
The complexes of hydrous copper chloride and copper nitrate with 2-amino-4,6-dimethylpyrimidine(ADMP) were prepared via reflux in alcohol. The compositions of the complexes were identified as Cu(ADMP) 2Cl 2·2H 2O...The complexes of hydrous copper chloride and copper nitrate with 2-amino-4,6-dimethylpyrimidine(ADMP) were prepared via reflux in alcohol. The compositions of the complexes were identified as Cu(ADMP) 2Cl 2·2H 2O(b) and Cu(ADMP)(NO 3) 2·H 2O(c) by chemical and elemental analyses. The complexes were characterized by IR, XPS, 1H NMR and TG-DTG techniques. The constant-volume combustion energies of ADMP and the complexes, Δ c E , were determined by a precise rotating-bomb calorimeter at 298 15 K. They were (-3664 53±1 18), (-4978 47±2 72) and (-1696 70±1 36) kJ/mol, respectively. Their standard enthalpies of combustion, Δ c H 0 m, and standard enthalpies of formation, Δ f H 0 m, were calculated to be (-3666 39±1 18), (-4977 23±2 72), (-1691 12±1 36) kJ/mol and (19 09±1 43), (-2041 80±3 29), (-2397 24±1 65) kJ/mol, respectively.展开更多
This paper reports the measurements of enthalpies of natural gas hydrates in typical natural gas mixture containing methane, ethane, propane and iso-butane at pressure in the vicinity of 2000 kPa (300 psi) and 6900 kP...This paper reports the measurements of enthalpies of natural gas hydrates in typical natural gas mixture containing methane, ethane, propane and iso-butane at pressure in the vicinity of 2000 kPa (300 psi) and 6900 kPa(1000psi). The measurements were made in a multi-cell differential scanning calorimeter using modified high pressure cells. The enthalpy of water and the enthalpy of dissociation of the gas hydrate were determined from the calorimeter response during slow temperature scanning at constant pressure. The amount of gas released from the dissociation of hydrate was determined from the pumped volume of the high pressure pump. The occupation ratio (mole ratio) of the water to gas and the enthalpy of hydrate formation are subject to uncertainty of 1.5%.The results show that the enthalpy of hydrate formation and the occupation ratio are essentially independent of pressure.展开更多
This paper reports that the low-temperature heat capacities of pyridine-2,6-dicarboxylic acid were measured by a precision automatic calorimeter over a temperature range from 78 K to 380 K. A polynomial equation of he...This paper reports that the low-temperature heat capacities of pyridine-2,6-dicarboxylic acid were measured by a precision automatic calorimeter over a temperature range from 78 K to 380 K. A polynomial equation of heat capacities as a function of temperature was fitted by the least-squares method. Based on the fitted polynomial, the smoothed heat capacities and thermodynamic functions of the compound relative to the standard reference temperature 298.15 K were calculated and tabulated at intervals of 5 K. The constant-volume energy of combustion of the compound was determined by means of a precision rotating-bomb combustion calorimeter. The standard molar enthalpy of combustion of the compound was derived from the constant-volume energy of combustion. The standard molar enthalpy of formation of the compound was calculated from a combination of the datum of the standard molar enthalpy of combustion of the compound with other auxiliary thermodynamic quantities through a Hess thermochemical cycle.展开更多
Standard enthalpies of formation of quasicrystalline phase and the ternary solid solutions in the Al-Fe-Cu system and the intermetaUic compound FeAI were determined by the means of solution calorimetry. The quasicryst...Standard enthalpies of formation of quasicrystalline phase and the ternary solid solutions in the Al-Fe-Cu system and the intermetaUic compound FeAI were determined by the means of solution calorimetry. The quasicrystalline phase was prepared using two different methods. The first method （I） consisted of ball milling the mixture of powders of pure aluminum copper and iron in a planetary mill with subsequent compacting by hot pressing and annealing. The second method （Ⅱ） consisted of arc melting of the components in argon atmosphere followed by annealing. The latter method was used for preparing the compound FeAl and the solid solutions. The phases were identified using the XRD method. The enthalpy of the formation was determined for the quasicrystalline phase of the composition Al62Cu25.5Fe12.5 and the temary BCC solid solutions Al35Cu14Fe51, Al40Cu17Fe43, and Al50.4Cu19.6Fe30. The measured enthalpy of formation of the intermetallic compound FeAl is in good agreement with the earlier published data. The enthalpies of formation of the quasicrystalline phases prepared using two different methods are close to each other, namely, -22.7±3.4 （method I） and -21.3±2.1 （method Ⅱ） kJ/mol.展开更多
Four solid ternary complexes of RE (C_5H_8NS_2)_3(C_(12)H_8N_2) (RE=Eu, Gd, Tb, Dy) were synthesized in absolute ethanol by rare earth chloride low hydrate with the mixed ligands of ammonium pyrrolidinedi-thiocarbamat...Four solid ternary complexes of RE (C_5H_8NS_2)_3(C_(12)H_8N_2) (RE=Eu, Gd, Tb, Dy) were synthesized in absolute ethanol by rare earth chloride low hydrate with the mixed ligands of ammonium pyrrolidinedi-thiocarbamate (APDC) and 1, 10-phenanthroline·H_2O (o-phen·H_2O) in the ordinary laboratory atmosphere without any cautions against moisture or air sensitivity. IR spectra of the complexes show that the RE^(3+) coordinated with six sulfur atoms of three PDC^- and two nitrogen atoms of o-phen·H_2O. It was assumed that the coordination number of RE^(3+) is eight. The constant-volume combustion energies of the complexes, Δ_cU, were determined as (-16937 88±9 79 ), (-17588 79±8 62 ), ((-17747 14±)8 25 ) and (-17840 37±8 87 ) kJ·mol^(-1), by a precise rotating-bomb calorimeter at 298.15 K. Its standard molar enthalpies of combustion, Δ_cH~θ_m, and standard molar enthalpies of formation, Δ_fH~θ_m, were calculated as (-16953 37±9 79), (-17604 28±8 62), (-17762 63±8 25), (-17855 86±8 87) kJ·mol^(-1) and (-857.04±10.52), (-282.43±9.58), (-130.08±9.13), (-55.75±9.83) kJ·mol^(-1).展开更多
The enthalpy of reaction for the decomposition of monoclinic ammonium paratungstate,(NH_4 )_10 H_2, W_12 O_424H_2 O(s), was measured using a HT-1000 calorimeter. From the experimentalresults, the standard enthalpy of ...The enthalpy of reaction for the decomposition of monoclinic ammonium paratungstate,(NH_4 )_10 H_2, W_12 O_424H_2 O(s), was measured using a HT-1000 calorimeter. From the experimentalresults, the standard enthalpy of formation of ammonium paratlingstate at 298.15 K is obtained.展开更多
This paper reports that 1-dodecylamine hydrobromide （1 C12H25NH3.Br）（s） has been synthesized using the liquid phase reaction method. The lattice potential energy of the compound 1-C12H25NH3.Br and the ionic vol- u...This paper reports that 1-dodecylamine hydrobromide （1 C12H25NH3.Br）（s） has been synthesized using the liquid phase reaction method. The lattice potential energy of the compound 1-C12H25NH3.Br and the ionic vol- ume and radius of the 1-C12H25NH3＋ cation are obtained from the crystallographic data and other auxiliary ther- modynamic data. The constant-volume energy of combustion of 1 C12H25NH3.Br（s） is measured to be AcUo（1 C12H25NH3.Br, s） = （7369.03-4-3.28） kJ.mo1-1 by means of an RBC-II precision rotating-bomb combustion calorime- ter at T=（298.15~0.001） K. The standard molar enthalpy of combustion of the compound is derived to be △cHo（1- C12H25NH3.Br, s）=- （7384.52±3.28） kJ.mo1-1 from the constant-volume energy of combustion. The standard molar enthalpy of formation of the compound is calculated to be △fHo（1-C12H25NH3.Br, s）=-（1317.86~3.67） kJ.mo1-1 from the standard molar enthalpy of combustion of the title compound and other auxiliary thermodynamic quantities through a thermochemical cycle.展开更多
Flavonols are plant nature. Morin and other related pigments that are ubiquitous in plant flavonols have come into recent prominence because of their usefulness as anticancer, antitumor, anti-AIDS, and other important...Flavonols are plant nature. Morin and other related pigments that are ubiquitous in plant flavonols have come into recent prominence because of their usefulness as anticancer, antitumor, anti-AIDS, and other important therapeutic activities of significant potency and low systemic toxicity. The heat of combustion of morin （molecular formula, C15H10O7·H2O） in oxygen was measured by a rotating-bomb type combustion calorimeter, the standard molar enthalpy of combustion of morin at T = 298.15 K was determined to be △cH^ m （C15H10O7·H2O, s） = - （5 937.99±2.99） kJ·mol^-1. The derived standard molar enthalpy of the formation of morin in solid powder state at T = 298.15 K, △fH^ m（C15H10O7·H2O, s）, was -（1 682.12 ± 3.58） kJ·mol^1, which provide an accurate data of the stability of morin to the pharmacy and pharmacology.展开更多
This paper reports that low-temperature heat capacities of 4-（2-aminoethyl）-phenol （C8H11NO） are measured by a precision automated adiabatic calorimeter over the temperature range from 78 to 400 K. A polynomial eq...This paper reports that low-temperature heat capacities of 4-（2-aminoethyl）-phenol （C8H11NO） are measured by a precision automated adiabatic calorimeter over the temperature range from 78 to 400 K. A polynomial equation of heat capacities as a function of the temperature was fitted by the least square method. Based on the fitted polynomial, the smoothed heat capacities and thermodynamic functions of the compound relative to the standard reference temperature 298.15K were calculated and tabulated at the interval of 5K. The energy equivalent, εcalor, of the oxygen-bomb combustion calorimeter has been determined from 0.68g of NIST 39i benzoic acid to be εcalor=（14674.69±17.49）J·K^-1. The constant-volume energy of combustion of the compound at T=298.15 K was measured by a precision oxygen-bomb combustion calorimeter to be ΔcU=-（32374.25±12.93）J·g^-1. The standard molar enthalpy of combustion for the compound was calculated to be ΔcHm = -（4445.47 ± 1.77） kJ·mol^-1 according to the definition of enthalpy of combustion and other thermodynamic principles. Finally, the standard molar enthalpy of formation of the compound was derived to be ΔfHm（C8H11NO, s）=-（274.68 ±2.06） kJ·mol^-1, in accordance with Hess law.展开更多
This paper reports that low-temperature heat capacities of N-methylnorephedrine C11H17NO（s） have been measured by a precision automated adiabatic calorimeter over the temperature range from T=78K to T=400K. A solid ...This paper reports that low-temperature heat capacities of N-methylnorephedrine C11H17NO（s） have been measured by a precision automated adiabatic calorimeter over the temperature range from T=78K to T=400K. A solid to liquid phase transition of the compound was found in the heat capacity curve in the temperature range of T=342-364 K. The peak temperature, molar enthalpy and entropy of fusion of the substance were determined. The experimental values of the molar heat capacities in the temperature regions of T=78-342 K and T=364-400 K were fitted to two poly- nomial equations of heat capacities with the reduced temperatures by least squares method. The smoothed molar heat capacities and thermodynamic functions of N-methylnorephedrine C11H17NO（s） relative to the standard refer- ence temperature 298.15 K were calculated based on the fitted polynomials and tabulated with an interval of 5 K. The constant-volume energy of combustion of the compound at T=298.15 K was measured by means of an isoperibol precision oxygen-bomb combustion calorimeter. The standard molar enthalpy of combustion of the sample was calculated. The standard molar enthalpy of formation of the compound was determined from the combustion enthalpy and other auxiliary thermodynamic data through a Hess thermochemical cycle.展开更多
118 kinds of Pt-Zr phases were established and investigated by considering various structures. Then the related physical properties, such as structural stability, lattice constants, formation enthalpies, elastic const...118 kinds of Pt-Zr phases were established and investigated by considering various structures. Then the related physical properties, such as structural stability, lattice constants, formation enthalpies, elastic constants and bulk moduli, are obtained by ab initio calculations. Based on the calculated results of formation enthalpies, the ground-state convex hull is derived for the Pt-Zr system. The calculated physical data would provide a basis for further thermodynamic calculations and atomistic simulations. For these Pt-Zr compounds, it is found there are a positive linear correlation between the formation enthalpies and atomic volumes, and a negative linear correlation between the bulk modules and atomic volumes.展开更多
The thermodynamic properties of different geometric structures of 1,2-cyclohexanediol which were rarely reported in literature, such as combustion enthalpy, formation enthalpy, melting enthalpy and heat ca-pacities, w...The thermodynamic properties of different geometric structures of 1,2-cyclohexanediol which were rarely reported in literature, such as combustion enthalpy, formation enthalpy, melting enthalpy and heat ca-pacities, were determined by NETZSCH DSC 204 Scanning Calorimeter. The relationship between the melting point and the composition for the mixture system of cis-1,2-cyclohexanediol and trans-1,2-cyclohexanediol was investigated and corresponding phase diagram was obtained. 'The melting enthalpies of both cis-1,2-cyclohexanediol and trans-1,2-cyclohexanediol are 20.265kJ·mol-1 and 16.368kJ·mol-1 respectively. The standard combustion enthalpies of cia- and trans-1,2-cyclohexaneddiol were determined by calorimeter. They are respec-tively -3507.043 kJ·mol-1 and - 3497.8 kJ·mol-1 at 298.15 K.The standard formation enthalpies are respectively 568.997 kJ·mol-1 and 578.240 kJ·mol-1 for cia- and trans -1,2-cyclohexaneddiol.展开更多
The parameters of embedded atom method for elements Ce, Th and Yb were determined by fitting the lattice constants, the cohesive energy, the monovacancy formation energy and the bulk modulus of elements. The alloy pot...The parameters of embedded atom method for elements Ce, Th and Yb were determined by fitting the lattice constants, the cohesive energy, the monovacancy formation energy and the bulk modulus of elements. The alloy potential was taken as the form of Johnson′s. The formation enthalpies of Th-Ce, Th-Yb and Ce-Yb binary alloys systems and Ce-Th-Yb ternary alloy were calculated with the present embedded atom potentials. The calculations for binary alloys are in good agreement with the results calculated with Miedema′s theory. As for the ternary alloy, the calculated formation enthalpies are in good agreement with those extrapolated from the formation enthalpies of constitutive binary alloys by Toop′s model.展开更多
A formulated as △fH m ? (PPDs,g)=a+ΣbiPi + cifi is put forward for estimating standard formation enthalpies of pyridine-derivatives (PDDs), in which,P i is path index andc i f i is an amended term of interac...A formulated as △fH m ? (PPDs,g)=a+ΣbiPi + cifi is put forward for estimating standard formation enthalpies of pyridine-derivatives (PDDs), in which,P i is path index andc i f i is an amended term of interaction between substituent and N atom on pyridine ring. The Calculations based on the model were carried out for some pyridine-derivatives. The values of standard formation enthalpy calculated are consistent with those in literature.展开更多
Balance solubility products and enthalpy of for- mation for NbC0.75, NbC0.85, NbC0.88, NbC and NbN in oriented silicon steels were calculated and compared quali- tatively. Meanwhile, the mixing enthalpies of these fiv...Balance solubility products and enthalpy of for- mation for NbC0.75, NbC0.85, NbC0.88, NbC and NbN in oriented silicon steels were calculated and compared quali- tatively. Meanwhile, the mixing enthalpies of these five Nb compounds were calculated based on Miedema Model. The results show that the solubility products of Nb compounds in ferrite and austenite meet the following relationship, NbC0.75 〉 NbC0.85 〉 NbC0.88 〉 NbC 〉 NbN and NbN has the minimum enthalpy of formation. It indicates that NbN easily precipitate out, but it is more difficult for NbC0.75.展开更多
The atomic structural parameter P-i = (Z(i)*/n(i)*) (1 + n(i)*/n(i)) (1 + m(i)/Z) and the molecular structural parameter [GRAPHICS] are defined. The standard formation enthalpies (Delta(f)H(m)(phi)) of 74 species of r...The atomic structural parameter P-i = (Z(i)*/n(i)*) (1 + n(i)*/n(i)) (1 + m(i)/Z) and the molecular structural parameter [GRAPHICS] are defined. The standard formation enthalpies (Delta(f)H(m)(phi)) of 74 species of rare earth compounds were studied with P, and the correlation coefficient is R > 0.94. The structural factors and the properties of rare earth compounds are influenced by the Z(i)*, n(i)*, n(i), m(i), Z. This study has special referential value to predict the properties of rare earth compounds.展开更多
'White powdery tungstic acid' has been used for preparing various types of tungsten-containing compounds due to its high reactivity. The present paper covers the standard molar enthalpies of formation, △H0/f ...'White powdery tungstic acid' has been used for preparing various types of tungsten-containing compounds due to its high reactivity. The present paper covers the standard molar enthalpies of formation, △H0/f of three tungsten- containing acids. The values found for 'white powdery tungstic acid' WO3·1. 68H2O, 'yellow tungstic acid' WO3·1. 20H2O and dodecatungstophosphoric acid H3(PW12O40)·25H2O at 298. 15 K were-(1312±1), - (1192±1) and -(18150±13) kJ mol-1, respectively.展开更多
Four solid complexes of rare earth isothiocyanates with glycine were synthesized. They were characterized by chemical analysis, elemental analysis, Infrared spectra, X-ray powder diffraction and TO-DSC analysis. Their...Four solid complexes of rare earth isothiocyanates with glycine were synthesized. They were characterized by chemical analysis, elemental analysis, Infrared spectra, X-ray powder diffraction and TO-DSC analysis. Their chemical formulae were proved to be RE(NCS)2.Gly .H2O, where RE is La, Ce, Pr or Nd. The integral heats of solution of RE(NCS)3.3Gly. H2O in water, of RE(NCS)2. 7H2O in aqueous glycine solution and of glycine in water have been measured calorimetricaliy at 298. 15K. By means of a thermochemical cycle suggested in this paper, the standard molar enthalpies of formation for RE(NCS)2. 3Gly.H2O(c) were obtained and their lattice energies were calculated.展开更多
基金Supported by the Hunan Provincial Educational Ministry Foundation(No.04C635)the Hunan Provincial Natural Sciences Foundation of China(No.08JJ3014)
文摘[Sm（C7H5O3）2（C4H6NO2S）]·2H2O was synthesized from the reaction of samarium chloride hexahydrate with salicylic acid and thioproline,and characterized by IR,elemental analysis and thermogravimatric analysis.The standard molar enthalpies of the solutions of SmCl3·6H2O（s）,2[C7H6O3（s）],[C4H7NO2S（s）] and [Sm（C7H5O3）2·（C4H6NO2S）·2H2O（s）] in a mixed solvent of absolute ethyl alcohol,dimethyl formamide（DMF） and 3 mol/L HCl were,respectively,determined by calorimetry to be ΔsHm^Θ [SmCl3·6H2O（s）,298.15 K]=（-46.68±0.15） kJ/mol,ΔsHm^Θ [2C7H6O3（s）,298.15 K]=（25.19±0.02） kJ/mol,ΔsHm^Θ [C4H7NO2S（s）,298.15 K]=（16.20±0.17） kJ/mol and ΔsHm^Θ {[Sm（C7H5O3）2（C4H6NO2S）]·2H2O（s）,298.15 K}=（-81.24±0.67） kJ/mol.The enthalpy change of the reaction SmCl3·6H2O（s）＋2C7H6O3（s）＋C4H7NO2S（s）=[Sm（C7H5O3）2（C4H6NO2S）]·2H2O（s）＋3HCl（g）＋4H2O（l） was determined to be ΔrHm^Θ =（123.45±0.71） kJ/mol.From the data in the literature,the standard molar formation enthalpy of [Sm（C7H5O3）2（C4H6NO2S）]·2H2O（s） was estimated to be Δf Hm^Θ {[Sm（C7H5O3）2（C4H6NO2S）]·2H2O（s）,298.15 K}=（-2912.03±3.1） kJ/mol through Hess＇ law.
文摘The relationship between temperature and oxygen vacancy concentration is deduced in this paper. Based on the data of thermal weight-loss experiment, the formation enthalpies of congruent and several doped LN crystals have been calculated. It was found that the formation enthalpy of oxygen vacancies can be decreased evidently by doping valence-changeable ions. The experimental results were discussed and a new reduction process of the photorefractive LN crystal at a relatively low temperature was proposed, and the reduced crystals showed a good effect in practical use.
基金Supported by the Education Ministry Foundation of Shaanxi Province(No.HF0 130 4 )
文摘The complexes of hydrous copper chloride and copper nitrate with 2-amino-4,6-dimethylpyrimidine(ADMP) were prepared via reflux in alcohol. The compositions of the complexes were identified as Cu(ADMP) 2Cl 2·2H 2O(b) and Cu(ADMP)(NO 3) 2·H 2O(c) by chemical and elemental analyses. The complexes were characterized by IR, XPS, 1H NMR and TG-DTG techniques. The constant-volume combustion energies of ADMP and the complexes, Δ c E , were determined by a precise rotating-bomb calorimeter at 298 15 K. They were (-3664 53±1 18), (-4978 47±2 72) and (-1696 70±1 36) kJ/mol, respectively. Their standard enthalpies of combustion, Δ c H 0 m, and standard enthalpies of formation, Δ f H 0 m, were calculated to be (-3666 39±1 18), (-4977 23±2 72), (-1691 12±1 36) kJ/mol and (19 09±1 43), (-2041 80±3 29), (-2397 24±1 65) kJ/mol, respectively.
文摘This paper reports the measurements of enthalpies of natural gas hydrates in typical natural gas mixture containing methane, ethane, propane and iso-butane at pressure in the vicinity of 2000 kPa (300 psi) and 6900 kPa(1000psi). The measurements were made in a multi-cell differential scanning calorimeter using modified high pressure cells. The enthalpy of water and the enthalpy of dissociation of the gas hydrate were determined from the calorimeter response during slow temperature scanning at constant pressure. The amount of gas released from the dissociation of hydrate was determined from the pumped volume of the high pressure pump. The occupation ratio (mole ratio) of the water to gas and the enthalpy of hydrate formation are subject to uncertainty of 1.5%.The results show that the enthalpy of hydrate formation and the occupation ratio are essentially independent of pressure.
基金Project supported by the National Natural Science Foundations of China (Grant Nos.20673050 and 20973089)
文摘This paper reports that the low-temperature heat capacities of pyridine-2,6-dicarboxylic acid were measured by a precision automatic calorimeter over a temperature range from 78 K to 380 K. A polynomial equation of heat capacities as a function of temperature was fitted by the least-squares method. Based on the fitted polynomial, the smoothed heat capacities and thermodynamic functions of the compound relative to the standard reference temperature 298.15 K were calculated and tabulated at intervals of 5 K. The constant-volume energy of combustion of the compound was determined by means of a precision rotating-bomb combustion calorimeter. The standard molar enthalpy of combustion of the compound was derived from the constant-volume energy of combustion. The standard molar enthalpy of formation of the compound was calculated from a combination of the datum of the standard molar enthalpy of combustion of the compound with other auxiliary thermodynamic quantities through a Hess thermochemical cycle.
文摘Standard enthalpies of formation of quasicrystalline phase and the ternary solid solutions in the Al-Fe-Cu system and the intermetaUic compound FeAI were determined by the means of solution calorimetry. The quasicrystalline phase was prepared using two different methods. The first method （I） consisted of ball milling the mixture of powders of pure aluminum copper and iron in a planetary mill with subsequent compacting by hot pressing and annealing. The second method （Ⅱ） consisted of arc melting of the components in argon atmosphere followed by annealing. The latter method was used for preparing the compound FeAl and the solid solutions. The phases were identified using the XRD method. The enthalpy of the formation was determined for the quasicrystalline phase of the composition Al62Cu25.5Fe12.5 and the temary BCC solid solutions Al35Cu14Fe51, Al40Cu17Fe43, and Al50.4Cu19.6Fe30. The measured enthalpy of formation of the intermetallic compound FeAl is in good agreement with the earlier published data. The enthalpies of formation of the quasicrystalline phases prepared using two different methods are close to each other, namely, -22.7±3.4 （method I） and -21.3±2.1 （method Ⅱ） kJ/mol.
基金Project supported by the Natural Science Foundation of China (2047104) and the Natural Science Foundation of Shaanxi Province (2003B19)
文摘Four solid ternary complexes of RE (C_5H_8NS_2)_3(C_(12)H_8N_2) (RE=Eu, Gd, Tb, Dy) were synthesized in absolute ethanol by rare earth chloride low hydrate with the mixed ligands of ammonium pyrrolidinedi-thiocarbamate (APDC) and 1, 10-phenanthroline·H_2O (o-phen·H_2O) in the ordinary laboratory atmosphere without any cautions against moisture or air sensitivity. IR spectra of the complexes show that the RE^(3+) coordinated with six sulfur atoms of three PDC^- and two nitrogen atoms of o-phen·H_2O. It was assumed that the coordination number of RE^(3+) is eight. The constant-volume combustion energies of the complexes, Δ_cU, were determined as (-16937 88±9 79 ), (-17588 79±8 62 ), ((-17747 14±)8 25 ) and (-17840 37±8 87 ) kJ·mol^(-1), by a precise rotating-bomb calorimeter at 298.15 K. Its standard molar enthalpies of combustion, Δ_cH~θ_m, and standard molar enthalpies of formation, Δ_fH~θ_m, were calculated as (-16953 37±9 79), (-17604 28±8 62), (-17762 63±8 25), (-17855 86±8 87) kJ·mol^(-1) and (-857.04±10.52), (-282.43±9.58), (-130.08±9.13), (-55.75±9.83) kJ·mol^(-1).
文摘The enthalpy of reaction for the decomposition of monoclinic ammonium paratungstate,(NH_4 )_10 H_2, W_12 O_424H_2 O(s), was measured using a HT-1000 calorimeter. From the experimentalresults, the standard enthalpy of formation of ammonium paratlingstate at 298.15 K is obtained.
基金supported by the National Natural Science Foundation of China (Grant Nos. 20673050 and 20973089)
文摘This paper reports that 1-dodecylamine hydrobromide （1 C12H25NH3.Br）（s） has been synthesized using the liquid phase reaction method. The lattice potential energy of the compound 1-C12H25NH3.Br and the ionic vol- ume and radius of the 1-C12H25NH3＋ cation are obtained from the crystallographic data and other auxiliary ther- modynamic data. The constant-volume energy of combustion of 1 C12H25NH3.Br（s） is measured to be AcUo（1 C12H25NH3.Br, s） = （7369.03-4-3.28） kJ.mo1-1 by means of an RBC-II precision rotating-bomb combustion calorime- ter at T=（298.15~0.001） K. The standard molar enthalpy of combustion of the compound is derived to be △cHo（1- C12H25NH3.Br, s）=- （7384.52±3.28） kJ.mo1-1 from the constant-volume energy of combustion. The standard molar enthalpy of formation of the compound is calculated to be △fHo（1-C12H25NH3.Br, s）=-（1317.86~3.67） kJ.mo1-1 from the standard molar enthalpy of combustion of the title compound and other auxiliary thermodynamic quantities through a thermochemical cycle.
基金Supported by the National Natural Science Foundation of China (30570015, 20621502)the Natural Science Foundation of Hubei Prov-ince (2005ABC002)the Research Foundation of Chinese Ministry of Edu-cation ([2006]8-IRT0543)
文摘Flavonols are plant nature. Morin and other related pigments that are ubiquitous in plant flavonols have come into recent prominence because of their usefulness as anticancer, antitumor, anti-AIDS, and other important therapeutic activities of significant potency and low systemic toxicity. The heat of combustion of morin （molecular formula, C15H10O7·H2O） in oxygen was measured by a rotating-bomb type combustion calorimeter, the standard molar enthalpy of combustion of morin at T = 298.15 K was determined to be △cH^ m （C15H10O7·H2O, s） = - （5 937.99±2.99） kJ·mol^-1. The derived standard molar enthalpy of the formation of morin in solid powder state at T = 298.15 K, △fH^ m（C15H10O7·H2O, s）, was -（1 682.12 ± 3.58） kJ·mol^1, which provide an accurate data of the stability of morin to the pharmacy and pharmacology.
基金supported by the National Natural Science Foundation of China (Grant No 20673050)
文摘This paper reports that low-temperature heat capacities of 4-（2-aminoethyl）-phenol （C8H11NO） are measured by a precision automated adiabatic calorimeter over the temperature range from 78 to 400 K. A polynomial equation of heat capacities as a function of the temperature was fitted by the least square method. Based on the fitted polynomial, the smoothed heat capacities and thermodynamic functions of the compound relative to the standard reference temperature 298.15K were calculated and tabulated at the interval of 5K. The energy equivalent, εcalor, of the oxygen-bomb combustion calorimeter has been determined from 0.68g of NIST 39i benzoic acid to be εcalor=（14674.69±17.49）J·K^-1. The constant-volume energy of combustion of the compound at T=298.15 K was measured by a precision oxygen-bomb combustion calorimeter to be ΔcU=-（32374.25±12.93）J·g^-1. The standard molar enthalpy of combustion for the compound was calculated to be ΔcHm = -（4445.47 ± 1.77） kJ·mol^-1 according to the definition of enthalpy of combustion and other thermodynamic principles. Finally, the standard molar enthalpy of formation of the compound was derived to be ΔfHm（C8H11NO, s）=-（274.68 ±2.06） kJ·mol^-1, in accordance with Hess law.
基金Project supported by the National Natural Science Foundation of China （Grant No 20673050）.
文摘This paper reports that low-temperature heat capacities of N-methylnorephedrine C11H17NO（s） have been measured by a precision automated adiabatic calorimeter over the temperature range from T=78K to T=400K. A solid to liquid phase transition of the compound was found in the heat capacity curve in the temperature range of T=342-364 K. The peak temperature, molar enthalpy and entropy of fusion of the substance were determined. The experimental values of the molar heat capacities in the temperature regions of T=78-342 K and T=364-400 K were fitted to two poly- nomial equations of heat capacities with the reduced temperatures by least squares method. The smoothed molar heat capacities and thermodynamic functions of N-methylnorephedrine C11H17NO（s） relative to the standard refer- ence temperature 298.15 K were calculated based on the fitted polynomials and tabulated with an interval of 5 K. The constant-volume energy of combustion of the compound at T=298.15 K was measured by means of an isoperibol precision oxygen-bomb combustion calorimeter. The standard molar enthalpy of combustion of the sample was calculated. The standard molar enthalpy of formation of the compound was determined from the combustion enthalpy and other auxiliary thermodynamic data through a Hess thermochemical cycle.
基金Projects (50971072,51131003) support by the National Natural Science Foundation of ChinaProjects (2011CB606301,2012CB825700) supported by the Ministry of Science and Technology of ChinaProject supported by the Administration of Tsinghua University
文摘118 kinds of Pt-Zr phases were established and investigated by considering various structures. Then the related physical properties, such as structural stability, lattice constants, formation enthalpies, elastic constants and bulk moduli, are obtained by ab initio calculations. Based on the calculated results of formation enthalpies, the ground-state convex hull is derived for the Pt-Zr system. The calculated physical data would provide a basis for further thermodynamic calculations and atomistic simulations. For these Pt-Zr compounds, it is found there are a positive linear correlation between the formation enthalpies and atomic volumes, and a negative linear correlation between the bulk modules and atomic volumes.
基金Natural Science Foundation of Henan Province(No.0211020800)
文摘The thermodynamic properties of different geometric structures of 1,2-cyclohexanediol which were rarely reported in literature, such as combustion enthalpy, formation enthalpy, melting enthalpy and heat ca-pacities, were determined by NETZSCH DSC 204 Scanning Calorimeter. The relationship between the melting point and the composition for the mixture system of cis-1,2-cyclohexanediol and trans-1,2-cyclohexanediol was investigated and corresponding phase diagram was obtained. 'The melting enthalpies of both cis-1,2-cyclohexanediol and trans-1,2-cyclohexanediol are 20.265kJ·mol-1 and 16.368kJ·mol-1 respectively. The standard combustion enthalpies of cia- and trans-1,2-cyclohexaneddiol were determined by calorimeter. They are respec-tively -3507.043 kJ·mol-1 and - 3497.8 kJ·mol-1 at 298.15 K.The standard formation enthalpies are respectively 568.997 kJ·mol-1 and 578.240 kJ·mol-1 for cia- and trans -1,2-cyclohexaneddiol.
文摘The parameters of embedded atom method for elements Ce, Th and Yb were determined by fitting the lattice constants, the cohesive energy, the monovacancy formation energy and the bulk modulus of elements. The alloy potential was taken as the form of Johnson′s. The formation enthalpies of Th-Ce, Th-Yb and Ce-Yb binary alloys systems and Ce-Th-Yb ternary alloy were calculated with the present embedded atom potentials. The calculations for binary alloys are in good agreement with the results calculated with Miedema′s theory. As for the ternary alloy, the calculated formation enthalpies are in good agreement with those extrapolated from the formation enthalpies of constitutive binary alloys by Toop′s model.
基金Supported by the National Natural Science Foundation of China!(29971024)
文摘A formulated as △fH m ? (PPDs,g)=a+ΣbiPi + cifi is put forward for estimating standard formation enthalpies of pyridine-derivatives (PDDs), in which,P i is path index andc i f i is an amended term of interaction between substituent and N atom on pyridine ring. The Calculations based on the model were carried out for some pyridine-derivatives. The values of standard formation enthalpy calculated are consistent with those in literature.
基金financially supported by the National Natural Science Foundation of China (Nos. 51274083 and 51074062)
文摘Balance solubility products and enthalpy of for- mation for NbC0.75, NbC0.85, NbC0.88, NbC and NbN in oriented silicon steels were calculated and compared quali- tatively. Meanwhile, the mixing enthalpies of these five Nb compounds were calculated based on Miedema Model. The results show that the solubility products of Nb compounds in ferrite and austenite meet the following relationship, NbC0.75 〉 NbC0.85 〉 NbC0.88 〉 NbC 〉 NbN and NbN has the minimum enthalpy of formation. It indicates that NbN easily precipitate out, but it is more difficult for NbC0.75.
文摘The atomic structural parameter P-i = (Z(i)*/n(i)*) (1 + n(i)*/n(i)) (1 + m(i)/Z) and the molecular structural parameter [GRAPHICS] are defined. The standard formation enthalpies (Delta(f)H(m)(phi)) of 74 species of rare earth compounds were studied with P, and the correlation coefficient is R > 0.94. The structural factors and the properties of rare earth compounds are influenced by the Z(i)*, n(i)*, n(i), m(i), Z. This study has special referential value to predict the properties of rare earth compounds.
文摘'White powdery tungstic acid' has been used for preparing various types of tungsten-containing compounds due to its high reactivity. The present paper covers the standard molar enthalpies of formation, △H0/f of three tungsten- containing acids. The values found for 'white powdery tungstic acid' WO3·1. 68H2O, 'yellow tungstic acid' WO3·1. 20H2O and dodecatungstophosphoric acid H3(PW12O40)·25H2O at 298. 15 K were-(1312±1), - (1192±1) and -(18150±13) kJ mol-1, respectively.
基金Projects supported by the National Natural Science Foundation of China.
文摘Four solid complexes of rare earth isothiocyanates with glycine were synthesized. They were characterized by chemical analysis, elemental analysis, Infrared spectra, X-ray powder diffraction and TO-DSC analysis. Their chemical formulae were proved to be RE(NCS)2.Gly .H2O, where RE is La, Ce, Pr or Nd. The integral heats of solution of RE(NCS)3.3Gly. H2O in water, of RE(NCS)2. 7H2O in aqueous glycine solution and of glycine in water have been measured calorimetricaliy at 298. 15K. By means of a thermochemical cycle suggested in this paper, the standard molar enthalpies of formation for RE(NCS)2. 3Gly.H2O(c) were obtained and their lattice energies were calculated.
