Low-temperature heat capacity and standard enthalpy of formation of neodymium glycine perchlorate complex [Nd2(Gly)6(H2O)4](ClO4)6·5H2O

Rare-earth perchlorate complex coordinated with glycine [Nd₂(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O was synthesized and its structure was characterized by using thermogravimetric analysis (TG), differential thermal analysis (DTA), chemical analysis and elementary analysis. Its purity was 99.90%. Heat capacity measurement was carried out with a high-precision fully-automatic adiabatic calorimeter over the temperature range from 78 to 369 K. A solid-solid phase transformation peak was observed at 256.97 K, with the enthalpy and entropy of the phase transformation process are 4.438 kJ mol⁻¹ and 17.270 J K⁻¹ mol⁻¹, respectively. There is a big dehydrated peak appears at 330 K, its decomposition temperature, decomposition enthalpy and entropy are 320.606 K, 41.364 kJ mol⁻¹ and 129.018 J K⁻¹ mol⁻¹, respectively. The polynomial equations of heat capacity of this compound in different temperature ranges have been fitted. The standard enthalpy of formation was determined to be −8023.002 kJ mol⁻¹ with isoperibol reaction calorimeter at 298.15 K.     

Heat capacities and thermodynamic properties of 2-benzoylpyridine (C12H9NO)

The heat capacities of 2-benzoylpyridine were measured with an automated adiabatic calorimeter over the temperature range from 80 to 340 K. The melting point, molar enthalpy, Δ_fusH^m, and entropy, Δ_fusS^m, of fusion of this compound were determined to be 316.49±0.04 K, 20.91±0.03 kJ mol^–1 and 66.07±0.05 J mol^–1 K^–1, respectively. The purity of the compound was calculated to be 99.60 mol% by using the fractional melting technique. The thermodynamic functions (H_T–H_298.15) and (S_T–S_298.15) were calculated based on the heat capacity measurements in the temperature range of 80–340 K with an interval of 5 K. The thermal properties of the compound were further investigated by differential scanning calorimetry (DSC). From the DSC curve, the temperature corresponding to the maximum evaporation rate, the molar enthalpy and entropy of evaporation were determined to be 556.3±0.1 K, 51.3±0.2 kJ mol^–1 and 92.2±0.4 J K^–1 mol^–1, respectively, under the experimental conditions.     

Thermochemical study of the solid complex Ho(PDC)3 (o-phen)

A novel solid complex, formulated as Ho(PDC)₃ (o-phen), has been obtained from the reaction of hydrate holmium chloride, ammonium pyrrolidinedithiocarbamate (APDC) and 1,10-phenanthroline (o-phen·H₂O) in absolute ethanol, which was characterized by elemental analysis, TG-DTG and IR spectrum. The enthalpy change of the reaction of complex formation from a solution of the reagents, Δ_rH_m^θ (sol), and the molar heat capacity of the complex, c_m, were determined as being –19.161±0.051 kJ mol^–1 and 79.264±1.218 J mol^–1 K^–1 at 298.15 K by using an RD-496 III heat conduction microcalorimeter. The enthalpy change of complex formation from the reaction of the reagents in the solid phase, Δ_rH_m^θ(s), was calculated as being (23.981±0.339) kJ mol^–1 on the basis of an appropriate thermochemical cycle and other auxiliary thermodynamic data. The thermodynamics of reaction of formation of the complex was investigated by the reaction in solution at the temperature range of 292.15–301.15 K. The constant-volume combustion energy of the complex, Δ_cU, was determined as being –16788.46±7.74 kJ mol^–1 by an RBC-II type rotating-bomb calorimeter at 298.15 K. Its standard enthalpy of combustion, Δ_cH_m^θ, and standard enthalpy of formation, Δ_fH_m^θ, were calculated to be –16803.95±7.74 and –1115.42±8.94 kJ mol^–1, respectively.     

Heat capacity,enthalpy and entropy of calcium niobates

Heat capacity and enthalpy increments of calcium niobates CaNb₂O₆ and Ca₂Nb₂O₇ were measured by the relaxation time method (2–300 K), DSC (260–360 K) and drop calorimetry (669–1421 K). Temperature dependencies of the molar heat capacity in the form C _pm=200.4+0.03432T−3.450·10⁶/T ² J K⁻¹ mol⁻¹ for CaNb₂O₆ and C _pm=257.2+0.03621T−4.435·10⁶/T ² J K⁻¹ mol⁻¹ for Ca₂Nb₂O₇ were derived by the least-squares method from the experimental data. The molar entropies at 298.15 K, S _m⁰(CaNb₂O₆, 298.15 K)=167.3±0.9 J K⁻¹ mol⁻¹ and S _m⁰(Ca₂Nb₂O₇, 298.15 K)=212.4±1.2 J K⁻¹ mol⁻¹, were evaluated from the low temperature heat capacity measurements. Standard enthalpies of formation at 298.15 K were derived using published values of Gibbs energy of formation and presented heat capacity and entropy data: Δ_f H ⁰(CaNb₂O₆, 298.15 K)= −2664.52 kJ mol^t-1 and Δ_f H ⁰(Ca₂Nb₂O₇, 298.15 K)= −3346.91 kJ mol⁻¹.     

Low-temperature thermodynamic properties of <Emphasis Type="SmallCaps">dl</Emphasis>-cysteine

Heat capacity C _p(T) of the crystalline dl-cysteine was measured on heating the system from 6 to 309 K by adiabatic calorimetry; thermodynamic functions were calculated based on these data smoothed in the temperature range 6–273.15 K. The values of heat capacity, entropy, and enthalpy at 273.15 K were equal to 142.4, 153.3, and 213.80 J K⁻¹ mol⁻¹, respectively. At about 300 K, a heat capacity peak was observed, which was interpreted as an evidence of a first-order phase transition. The enthalpy and the entropy of the transition are equal, respectively, to 2300 ± 50 and 7.6 ± 0.1 J K⁻¹ mol⁻¹.     

Low-temperature thermodynamic properties of <Emphasis Type="Italic">L</Emphasis>-cysteine

Heat capacity C _p(T) of the orthorhombic polymorph of L-cysteine was measured in the temperature range 6–300 K by adiabatic calorimetry; thermodynamic functions were calculated based on these measurements. At 298.15 K the values of heat capacity, C _p; entropy, S _m⁰(T)-S _m⁰(0); difference in the enthalpy, H _m⁰(T)-H _m⁰(0), are equal, respectively, to 144.6±0.3 J K⁻¹ mol⁻¹, 169.0±0.4 J K⁻¹ mol⁻¹ and 24960±50 J mol⁻¹. An anomaly of heat capacity near 70 K was registered as a small, 3–5% height, diffuse ‘jump’ accompanied by the substantial increase in the thermal relaxation time. The shape of the anomaly is sensitive to thermal pre-history of the sample.     

Thermodynamic investigation of room temperature ionic liquid

The molar heat capacities of the room temperature ionic liquid 1-butylpyridinium tetrafluoroborate (BPBF₄) were measured by an adiabatic calorimeter in temperature range from 80 to 390 K. The dependence of the molar heat capacity on temperature is given as a function of the reduced temperature X by polynomial equations, C _p,m [J K⁻¹ mol⁻¹]=181.43+51.297X −4.7816X ²−1.9734X ³+8.1048X ⁴+11.108X ⁵ [X=(T−135)/55] for the solid phase (80–190 K), C _p,m [J K⁻¹ mol⁻¹]= 349.96+25.106X+9.1320X ²+19.368X ³+2.23X ⁴−8.8201X ⁵ [X=(T−225)/27] for the glass state (198–252 K), and C _p,m[J K⁻¹ mol⁻¹]= 402.40+21.982X−3.0304X ²+3.6514X ³+3.4585X ⁴ [X=(T−338)/52] for the liquid phase (286–390 K), respectively. According to the polynomial equations and thermodynamic relationship, the values of thermodynamic function of the BPBF₄ relative to 298.15 K were calculated in temperature range from 80 to 390 K with an interval of 5 K. The glass transition of BPBF₄ was observed at 194.09 K, the enthalpy and entropy of the glass transition were determined to be ΔH _g=2.157 kJ mol⁻¹ and ΔS _g=11.12 J K⁻¹ mol⁻¹, respectively. The result showed that the melting point of the BPBF₄ is 279.79 K, the enthalpy and entropy of phase transition were calculated to be ΔH _m = 8.453 kJ mol⁻¹ and ΔS _m=30.21 J K⁻¹ mol⁻¹. Using oxygen-bomb combustion calorimeter, the molar enthalpy of combustion of BPBF₄ was determined to be Δ_c H _m⁰ = −5451±3 kJ mol⁻¹. The standard molar enthalpy of formation of BPBF₄ was evaluated to be Δ_f H _m⁰ = −1356.3±0.8 kJ mol⁻¹ at T=298.150±0.001 K.     

Thermodynamic Properties of Hydrofullerene C60H36 from 5 to 340 K

The temperature dependence of the molar heat capacity (C⁰ _p) of hydrofullerene C₆₀H₃₆ between 5 and 340 K was determined by adiabatic vacuum calorimetry with an error of about 0.2%. The experimental data were used for the calculation of the thermodynamic functions of the compound in the range 0 to340 K. It was found that at T=298.15 K and p=101.325 kPa C⁰ _p (298.15)=690.0 J K⁻¹ mol⁻¹,H^o(298.15)−H^o(0)= 84.94 kJ mol⁻¹,S^o(298.15)=506.8 J K⁻¹ mol⁻¹, G^o(298.15)−H^o(0)= −66.17 kJ mol⁻¹. The standard entropy of formation of hydrofullerene C₆₀H₃₆ and the entropy of reaction of its formation by hydrogenation of fullerene C₆₀ with hydrogen were estimated and at T=298.15 K they were Δ_fS^o= −2188.4 J K⁻¹ mol⁻¹ and Δ_rS^o= −2270.5 J K⁻¹mol⁻¹, respectively. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermochemistry of europium and dithiocarbamate complex Eu(C5H8NS2)3(C12H8N2)

A solid complex Eu(C₅H₈NS₂)₃(C₁₂H₈N₂) has been obtained from reaction of hydrous europium chloride with ammonium pyrrolidinedithiocarbamate (APDC) and 1,10-phenanthroline (o-phen⋅H₂O) in absolute ethanol. IR spectrum of the complex indicated that Eu³⁺ in the complex coordinated with sulfur atoms from the APDC and nitrogen atoms from the o-phen. TG-DTG investigation provided the evidence that the title complex was decomposed into EuS. The enthalpy change of the reaction of formation of the complex in ethanol, Δ_r H _m ^θ(l), as –22.214±0.081 kJ mol^–1, and the molar heat capacity of the complex, c _m, as 61.676±0.651 J mol^–1 K^–1, at 298.15 K were determined by an RD-496 III type microcalorimeter. The enthalpy change of the reaction of formation of the complex in solid, Δ_r H _m ^θ(s), was calculated as 54.527±0.314 kJ mol^–1 through a thermochemistry cycle. Based on the thermodynamics and kinetics on the reaction of formation of the complex in ethanol at different temperatures, fundamental parameters, including the activation enthalpy (ΔH _≠ ^θ), the activation entropy (ΔS _≠ ^θ), the activation free energy (ΔG _≠ ^θ), the apparent reaction rate constant (k), the apparent activation energy (E), the pre-exponential constant (A) and the reaction order (n), were obtained. The constant-volume combustion energy of the complex, Δ_c U, was determined as –16937.88±9.79 kJ mol^–1 by an RBC-II type rotating-bomb calorimeter at 298.15 K. Its standard enthalpy of combustion, Δ_c H _m ^θ, and standard enthalpy of formation, Δ_f H _m ^θ, were calculated to be –16953.37±9.79 and –1708.23±10.69 kJ mol^–1, respectively.     

Thermodynamics of the conversion of aqueous glucose to fructose

The thermodynamics of the conversion of aqueous glucose to fructose has been investigated using both heat conduction microcalorimetry and high pressure liquid chromatography (HPLC). The reaction was carried out in both aqueous Tris/HCl buffer and in aqueous phosphate buffer in the pH range 7–8 using the enzyme glucose isomerase and the cofactors CoCl₂ and MgSO₄. The temperature range over which this reaction was investigated was 298.15–358.15 K. We have found that the enthalpy of reaction is independent of pH over the range investigated. A combined analysis of both the HPLC and microcalorimetric data leads to the following results at 298 15 K:ΔG° = 349 ± 53 J mol^-1, ΔH° = 2.78 ± 0.20 kJ mol^-1, and ΔC _p ^° = 76 ± 30 J mol^-1 K^-1. The stated uncertainties are based upon an analysis of both the random and systematic errors inherent in the measurements. Comparisons are made with literature data. The percent conversion of glucose to fructose has been calculated for the temperature range 300–373.15 K.     

Preparation and characterization of anion-cation surfactants modified montmorillonite

The low-temperature molar heat capacities of CoPc and CoTMPP were measured by temperature modulated differential scanning calorimetry (TMDSC) over the temperature range from 223 to 413 K for the first time. No phase transition or thermal anomaly was observed in the experimental temperature range for CoPc. However, a structural change was found to be nonreversible for CoTMPP in the temperature range of 368–403 K, which was further validated by the results of IR and XRD. The molar enthalpy ΔH _m and entropy ΔS _m of phase transition of the CoTMPP were determined to be 3.301 kJ mol⁻¹ and 8.596 J K⁻¹ mol⁻¹, respectively. The thermodynamic parameters of CoPc and CoTMPP such as entropy and enthalpy relative to reference temperature 298.15 K were derived based on the above molar heat capacity data. Moreover, the thermal stability of these two compounds was further investigated through TG measurements. Three steps of mass loss were observed in the TG curve for CoPc and five steps for CoTMPP.     

Thermodynamic investigation of room temperature ionic liquid

The molar heat capacities of the room temperature ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMIBF₄) were measured by an adiabatic calorimeter in temperature range from 80 to 390 K. The dependence of the molar heat capacity on temperature is given as a function of the reduced temperature X by polynomial equations, C _P,m (J K^–1 mol^–1)= 195.55+47.230 X–3.1533 X ²+4.0733 X ³+3.9126 X ⁴ [X=(T–125.5)/45.5] for the solid phase (80~171 K), and C _P,m (J K^–1 mol^–1)= 378.62+43.929 X+16.456 X ²–4.6684 X ³–5.5876 X ⁴ [X=(T–285.5)/104.5] for the liquid phase (181~390 K), respectively. According to the polynomial equations and thermodynamic relationship, the values of thermodynamic function of the BMIBF₄ relative to 298.15 K were calculated in temperature range from 80 to 390 K with an interval of 5 K. The glass translation of BMIBF₄ was observed at 176.24 K. Using oxygen-bomb combustion calorimeter, the molar enthalpy of combustion of BMIBF₄ was determined to be Δ_c H _m ^o= – 5335±17 kJ mol^–1. The standard molar enthalpy of formation of BMIBF₄ was evaluated to be Δ_f H _m ^o= –1221.8±4.0 kJ mol^–1 at T=298.150±0.001 K.     

Temperature dependence of the thermodynamic parameters of cobalt(II) clathrochelate: X-ray diffraction and calorimetric characteristics of the low temperature structural phase transition

The temperature dependence of heat capacity of the polycrystalline sample of cobalt(II) clathrochelate in a range of 6–300 K is studied. Based on the smoothed dependence C _p(T), the entropy and enthalpy values in a temperature range of 8–300 K and their standard values at 298.15 K are calculated. In the C _p(T) curve in a range of 50–70 K, a process is recorded whose entropy and enthalpy are 1.2 J·(K·mol⁻¹) and 68 J·mol⁻¹ respectively. A comparison of the results with the data of a multitemperature X-ray diffraction study makes it possible to attribute this process to the structural phase transition.     

Heat capacity of methacetin in a temperature range of 6 to 300 K

Heat capacity of methacetin (N-(4-methoxyphenyl)-acetamide) has been measured in the temperature range 5.8–300 K. No anomalies in the C _p(T) dependence were observed. Thermodynamic functions were calculated. At 298.15 K, the values of entropy and enthalpy are equal to 243.1 J K⁻¹ mol⁻¹ and 36360 J mol⁻¹, respectively. The heat capacity of methacetin in the temperature range 6–10 K is well fitted by Debye equation C _p = AT ³. The thermodynamic data obtained for methacetin are compared with those for the monoclinic and orthorhombic polymorphs of paracetamol.     

Thermodynamic characteristics of thermal dissociation of platinum dichloride

The dissociation pressure for the process PtCl₂(s) → Pt(s) + Cl₂(g) was measured by the static method with diaphragm zero-pressure gauges. The approximating equation for the temperature dependence on the dissociation pressure for the above reaction was found. The enthalpy (137.7±0.3 kJ mol⁻¹) and entropy (163.6±0.4 J mol⁻¹ K⁻¹) of PtCl₂(s) dissociation and enthalpies of formation and absolute entropies of platinum di- and trichlorides at 298.15 K were calculated. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1345–1348, June, 2005.     

Thermodynamic properties of strontium metaniobate SrNb<Subscript>2</Subscript>O<Subscript>6</Subscript>

The heat capacity and the enthalpy increments of strontium metaniobate SrNb₂O₆ were measured by the relaxation method (2-276 K), micro DSC calorimetry (260-320 K) and drop calorimetry (723-1472 K). Temperature dependence of the molar heat capacity in the form C _pm=(200.47±5.51)+(0.02937±0.0760)T-(3.4728±0.3115)·10⁶/T ² J K⁻¹ mol⁻¹ (298-1500 K) was derived by the least-squares method from the experimental data. Furthermore, the standard molar entropy at 298.15 K S _m⁰ (298.15 K)=173.88±0.39 J K⁻¹ mol⁻¹ was evaluated from the low temperature heat capacity measurements. The standard enthalpy of formation Δ_f H ⁰ (298.15 K)=-2826.78 kJ mol⁻¹ was derived from total energies obtained by full potential LAPW electronic structure calculations within density functional theory.     

Low temperature heat capacity of the coordination compound: Nickel(II) nitrate with 4-amine-1,2,4-triazole at temperatures from 11 to 317 K

Low-temperature heat capacity of the coordination compound of nickel(II) nitrate with 4-amine-1,2,4-triazole was measured in the temperature range from 11 to 317 K using a computerized vacuum adiabatic calorimeter. The thermodynamic functions have been derived from the smoothed experimental data over the whole temperature interval covered and at standard conditions. At 298.15 K, the heat capacity is 574.7±1.2 J K^-1 mol^-1, the entropy is 599.2±1.2 J K^-1 mol^-1, the enthalpy is 91070±200 J mol^-1, and the reduced Gibbs energy is 293.7±1.2 J K^-1 mol^-1. The results on C_p(T) were compared with those for Cu(NH₂trz)₃(NO₃)₂·0.5H₂O. It was revealed that the slope of the curve dC_p/dT (T) changes essentially for both compounds at 110-120 K. It implies that additional degrees of freedom appear in the heat capacity at these temperatures.This revised version was published online in November 2005 with corrections to the Cover Date.     

Heat capacity and heat content of BiNb<Subscript>5</Subscript>O<Subscript>14</Subscript>

The heat capacity and the heat content of bismuth niobate BiNb₅O₁₄ were measured by the relaxation time method, DSC and drop method, respectively. The temperature dependence of heat capacity in the form C _pm=455.84+0.06016T–7.7342·10⁶/T ² (J K^–1 mol^–1) was derived by the least squares method from the experimental data. Furthermore, the standard molar entropy at 298.15 K S _m=397.17 J K^–1 mol^–1 was derived from the low temperature heat capacity measurement.     

Thermodynamic investigation of several natural polyols

The low-temperature heat capacity C _p,m of erythritol (C₄H₁₀O₄, CAS 149-32-6) was precisely measured in the temperature range from 80 to 410 K by means of a small sample automated adiabatic calorimeter. A solid-liquid phase transition was found at T=390.254 K from the experimental C _p-T curve. The molar enthalpy and entropy of this transition were determined to be 37.92±0.19 kJ mol⁻¹ and 97.17±0.49 J K⁻¹ mol⁻¹, respectively. The thermodynamic functions [H _T-H _298.15] and [S _T-S _298.15], were derived from the heat capacity data in the temperature range of 80 to 410 K with an interval of 5 K. The standard molar enthalpy of combustion and the standard molar enthalpy of formation of the compound have been determined: Δ_c H _m⁰(C₄H₁₀O₄, cr)= −2102.90±1.56 kJ mol⁻¹ and Δ_f H _m⁰(C₄H₁₀O₄, cr)= − 900.29±0.84 kJ mol⁻¹, by means of a precision oxygen-bomb combustion calorimeter at T=298.15 K. DSC and TG measurements were performed to study the thermostability of the compound. The results were in agreement with those obtained from heat capacity measurements.     

Molar heat capacities and standard molar enthalpy of formation of 2-amino-5-methylpyridine

The heat capacities (C _p,m) of 2-amino-5-methylpyridine (AMP) were measured by a precision automated adiabatic calorimeter over the temperature range from 80 to 398 K. A solid-liquid phase transition was found in the range from 336 to 351 K with the peak heat capacity at 350.426 K. The melting temperature (T _m), the molar enthalpy (Δ_fus H _m⁰), and the molar entropy (Δ_fus S _m⁰) of fusion were determined to be 350.431±0.018 K, 18.108 kJ mol⁻¹ and 51.676 J K⁻¹ mol⁻¹, respectively. The mole fraction purity of the sample used was determined to be 0.99734 through the Van’t Hoff equation. The thermodynamic functions (H _T-H _298.15 and S _T-S _298.15) were calculated. The molar energy of combustion and the standard molar enthalpy of combustion were determined, ΔU _c(C₆H₈N₂,cr)= −3500.15±1.51 kJ mol⁻¹ and Δ_c H _m⁰ (C₆H₈N₂,cr)= −3502.64±1.51 kJ mol⁻¹, by means of a precision oxygen-bomb combustion calorimeter at T=298.15 K. The standard molar enthalpy of formation of the crystalline compound was derived, Δ_r H _m⁰ (C₆H₈N₂,cr)= −1.74±0.57 kJ mol⁻¹.