Low‐Temperature Heat Capacities and Standard Molar Enthalpy of Formation of Gramine (C11H14N2)

Low‐temperature heat capacities of gramine (C₁₁H₁₄N₂) were measured by a precision automated adiabatic calorimeter over the temperature range from 78 to 401 K. A polynomial equation of heat capacities as a function of temperature was fitted by 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 5 K intervals. The constant‐volume energy of combustion of the compound at T=298.15 K was measured by a precision oxygen‐bomb combustion calorimeter as Δ_cU=−(35336.7±13.9) J·g⁻¹. The standard molar enthalpy of combustion of the compound was determined to be Δ_cH_m⁰=−(6163.2±2.4) kJ·mol⁻¹, according to the definition of combustion enthalpy. Finally, the standard molar enthalpy of formation of the compound was calculated to be Δ;_cH_m⁰=−(166.2±2.8) kJ·mol⁻¹ in accordance with Hess law.     

Heat capacity of poly(vinyl methyl ether)

The heat capacity of poly(vinyl methyl ether) (PVME) has been measured using adiabatic calorimetry and temperature‐modulated differential scanning calorimetry (TMDSC). The heat capacity of the solid and liquid states of amorphous PVME is reported from 5 to 360 K. The amorphous PVME has a glass transition at 248 K (?25 °C). Below the glass transition, the low‐temperature, experimental heat capacity of solid PVME is linked to the vibrational molecular motion. It can be approximated by a group vibration spectrum and a skeletal vibration spectrum. The skeletal vibrations were described by a general Tarasov equation with three Debye temperatures Θ₁ = 647 K, Θ₂ = Θ₃ = 70 K, and nine skeletal modes. The calculated and experimental heat capacities agree to better than ±1.8% in the temperature range from 5 to 200 K. The experimental heat capacity of the liquid rubbery state of PVME is represented by C_p(liquid) = 72.36 + 0.136 T in J K^?1 mol^?1 and compared to estimated results from contributions of the same constituent groups of other polymers using the Advanced Thermal AnalysiS (ATHAS) Data Bank. The calculated solid and liquid heat capacities serve as baselines for the quantitative thermal analysis of amorphous PVME with different thermal histories. Also, knowing C_p of the solid and liquid, the integral thermodynamic functions of enthalpy, entropy, and free enthalpy of glassy and amorphous PVME are calculated with help of estimated parameters for the crystal. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2141–2153, 2005     

Crystal Structure, Phase Transition, and Thermodynamic Properties of Bis-dodecylammonium Tetrachlorozincate (C12H25NH3)2ZnCl4(s)

The crystal structure and composition of (C₁₂H₂₅NH₃)₂ZnCl₄(s) were characterized by chemical and elemental analysis, X‐ray powder diffraction technique and X‐ray crystallography. The lattice energy of the title compound was calculated to be U_POT=888.82 kJ·mol^?1. Low temperature heat capacities of the title compound have been measured by a precision automated adiabatic calorimeter over the temperature range from 80 to 403 K. An obvious solid to solid phase transition occurred in the heat capacity curve, and the peak temperature, molar enthalpy and molar entropy of the phase transition of the compound were determined to be T_trs= (364.02±0.03) K, (_trsH_m= (77.567±0.341) kJ·mol^?1, and (_trsS_m= (213.77±1.17) J·K^?1·mol^?1, respectively. Experimental molar heat capacities before and after the phase transition were respectively fitted to two polynomial equations. The smoothed molar heat capacities and fundamental thermodynamic functions of the sample relative to the standard reference temperature 298.15 K were calculated and tabulated at an interval of 5 K.     

烟酸的低温热容和标准摩尔生成焓

利用精密自动绝热热量计测量了分析纯烟酸在78～400 K温区的低温热容. 用最小二乘法将实验摩尔热容对温度进行拟合, 得到了热容随温度变化的多项式方程. 用此方程进行数值积分, 得到在此温区每隔5 K的舒平热容值和相对于298.15 K时的热力学函数值. 利用精密静止氧弹燃烧热量计测定了烟酸在298.15 K时的恒体积燃烧能为 Δ_cU＝ －(24528.3±16.1) J•g^－1. 依据物质燃烧焓定义计算出烟酸的标准摩尔燃烧焓为: Δ_cH_m^o＝－(3019.05±1.98) kJ•mol^－1. 最后, 依据Hess定律计算出烟酸的标准摩尔生成焓为: Δ_fH_m^o＝－(56.76±2.13) kJ•mol^－1.     

Low-Temperature Heat Capacities and Thermodynamic Properties of Octahydrated Barium Dihydroxide,Ba（OH）2·8H2O（s）

Low-temperature heat capacities of octahydrated barium dihydroxide, Ba（OH）2·8H2O（s）, were measured by a precision automated adiabatic calorimeter in the temperature range from T=78 to 370 K. An obvious endothermic process took place in the temperature range of 345-356 K. The peak in the heat capacity curve was correspondent to the sum of both the fusion and the first thermal decomposition or dehydration. The experimental molar heat capacifies in the temperature ranges of 78-345 K and 356-369 K were fitted to two polynomials. The peak temperature, molar enthalpy and entropy of the phase change have been determined to be （355.007±0.076） K, （73.506±0.011） kJ·ol^-1 and （207.140±0.074） J·K^-1·mol^-1, respectively, by three series of repeated heat capacity measurements in the temperature region of 298-370 K. The thermodynamic functions, （Hr-H298.15 k ）and （Sr-S298.15k）, of the compound have been calculated by the numerical integral of the two heat-eapacity polynomials. In addition, DSC and TG-DTG techniques were used for the further study of thermal behavior of the compound. The latent heat of the phase change became into a value larger than that of the normal compound because the melfing process of the compound must be accompanied by the thermal decomposition or dehydration of 71-120.     

Thermodynamic and kinetic behaviour of salicylsalicylic acid

The thermal behaviour of salicylsalicylic acid (CAS number 552-94-3) was studied by differential scanning calorimetry (DSC). The endothermic melting peak and the fingerprint of the glass transition were characterised at a heating rate of 10°C min^-1. The melting peak showed an onset at T _on = 144°C (417 K) and a maximum intensity at T _max = 152°C (425 K), while the onset of the glass transition signal was at T _on = 6°C. The melting enthalpy was found to be Δ_mH = 28.9±0.3 kJ mol^-1, and the heat capacity jump at the glass transition was ΔC _P = 108.1±0.1 J K^-1mol^-1. The study of the influence of the heating rate on the temperature location of the glass transition signal by DSC, allowed the determination of the activation energy at the glass transition temperature (245 kJ mol^-1), and the calculation of the fragility index of salicyl salicylate (m = 45). Finally, the standard molar enthalpy of formation of crystalline monoclinic salicylsalicylic acid at T = 298.15 K, was determined as Δ_fH_m ^o(C₁₄H₁₀O₅, cr) = - (837.6±3.3) kJ mol^-1, by combustion calorimetry. This revised version was published online in August 2006 with corrections to the Cover Date.     

水合烟酸铜Cu(Nic)2•H2O(s)(Nic＝烟酸)的合成、表征及热力学性质

近几十年来,烟酸盐类化合物或配合物由于优越的吸收率高和无毒副作用等特点使其在化妆品、药品和食品等领域作为营养添加剂具有重要应用前景。然而,这类化合物的基础热力学数据极其缺乏,从而限制了这类化合物的理论研究和应用开发的深入开展。为此,本论文利用室温固相合成方法和球磨技术合成了一种新化合物Cu(Nic)2•H2O(s),利用化学分析、元素分析、FTIR和X-射线粉末衍射技术表征了它的结构和组成,利用精密自动绝热热量计准确地测量了它在78-400 K温区的摩尔热容。在热容曲线的T ＝ 326-346 K温区观察到一个明显的固-液相变过程。利用相变温区三次重复实验热容的测量结果确定了此相变过程的峰温、相变焓和相变熵分别为：Tfus＝(341.290 ±0.873) K, DfusHm＝(13.582±0.012) kJ×mol-1, DfusSm＝(39.797±0.067) J×K-1×mol-1。通过最小二乘法将相变前和相变后的热容实验值分别拟合成了热容对温度的两个多项式方程。通过热容多项式方程的数值积分,得到了这个化合物的舒平热容值和相对于298.15 K的各种热力学函数值,并且将每隔5 K的热力学函数值列成了表格。     

Thermodynamic properties of α-platinum dichloride

The heat capacity of crystalline α-platinum dichloride was measured for the first time in the temperature intervals from 11 to 300 K (vacuum adiabatic microcalorimeter) and from 300 to 620 K (differential scanning calorimetry). In the 300–620 K temperature interval, the C° _p values for α-PtCl₂ (cr) coincide with the heat capacity of CrCl₂ (cr) within the limits of experimental error, which made it possible to estimate the heat capacity of α-PtCl₂ (cr) at higher temperatures. The approximating equation of the temperature dependence of the heat capacity in the interval from 298 to 900 K C° _p (±0.8) = 63.5 + 21.4·10⁻³ T + 0.883·10⁵/T ² (J mol⁻¹ K⁻¹) was derived using the experimental values, as well as the literature data on the heat capacity of CrCl₂ (cr). For the standard conditions, the C° _p,298.15 and S°_298.15 values are 70.92±0.08 and 100.9±0.33 J mol⁻¹ K, respectively; H°_298.15 − H°₀ = 14 120±42 J mol⁻¹. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1136–1138, June, 2008.     

Low-Temperature Heat Capacities and Thermodynamic Properties of Hydrated Nickel L-Threonate Ni（C4H7O5）2·2H2O（S）

Low-temperature heat capacities of the compound Ni（C4H7O5）2·2H2O（S） have been measured with an auto- mated adiabatic calorimeter. A thermal decomposition or dehydration occurred in 350--369 K. The temperature, the enthalpy and entropy of the dehydration were determined to be （368.141 ±0.095） K, （18.809±0.088） kJ·mol ^-1 and （51.093±0.239） J·K^-1·mol^-1 respertively. The experimental values of the molar heat capacities in the temperature regions of 78-350 and 368-390 K were fitted to two polynomial equations of heat capacities （Cp,m） with the reduced temperatures （X）, [X=f（T）], by a least squares method, respectively. The smoothed molar heat capacities and thermodynamic functions of the compound were calculated on the basis of the fitted polynomials. The smoothed values of the molar heat capacities and fundamental thermodynamic functions of the sample relative to the standard reference temperature 298.15 K were tabulated with an interval of 5 K.     

Synthesis,Characterization and Thermodynamic Study of the Solid State Coordination Compound Ni(Nic)2·H2O(s)(Nic=Nicotinate)

A novel compound‐monohydrated nickel nicotinate was synthesized by the method of room temperature solid phase synthesis and ball grinder. FTIR, chemical and elemental analysis, TG/DTG, and X‐ray powder diffraction technique were applied to characterize the structure and composition of the coordination compound. Low‐temperature heat capacities of the solid coordination compound have been measured by a precision automated adiabatic calorimeter over the temperature range from 78 to 386 K. A solid‐solid phase transition occurred in the temperature range of 328–358 K in the heat capacity curve, and the peak temperature, the molar enthalpy and molar entropy of the phase transition were determined to be T_trs=(356.759±0.697) K, Δ_trsH_m=(13.650±0.408) kJ· mol^?1, and Δ_trsS_m= (38.279±0.086) J·K^?1·mol^?1, respectively. The experimental values of the molar heat capacities in the temperature ranges of 78–328 K and 358–386 K were fitted to two polynomials, respectively. The polynomial fitted values of the molar heat capacities and fundamental thermodynamic functions of the sample relative to the standard reference temperature 298.15 K were calculated and tabulated at the intervals of 5 K.     

Etude thermique et thermodynamique du cyclohexaphosphate de lithium Li6P6O18·5H2O

We report in this paper the results of our thermal and thermodynamic investigation on lithium cyclohexaphosphate, Li₆P₆O₁₈·5H₂O between 298 and 1007 K. The different transitions with respect to temperature (successive dehydrations, solid-solid transition and melting) were studied with the help of differential thermal analysis and thermogravimetry. The different phases were characterized by X-ray diffraction and by infrared absorption. Finally, the enthalpy of these phasesvs. temperature was measured by isothermal drop calorimetry. Their heat capacities as well as the enthalpies of dehydration, of solid-solid transition and of melting were deduced. We pointed out that the lithium cyclohexaphosphate loses a molecule of water at 333 K (54.3 kJ·mol^?1), three molecules of water at 413 K (151 kJ·mol^?1) and the last one at 488 K (50.6 kJ·mol^?1). The anhydrous lithium cyclohexaphosphate, Li₆P₆O₁₈, give the polyphosphate, LiPO₃, at 708 K (second order transition) and melt at 933 K (24.6 kJ·mol^?1).     

Enthalpies of Phase Transitions and Heat Capacity of TbCl3 and Compounds Formed in TbCl3–MCl Systems (M=K, Rb, Cs)

The molar enthalpies of the solid–solid and solid–liquid phase transitions were determined by differential scanning calorimetry for pure TbCl₃ and KTb₂Cl₇, RbTb₂Cl₇, CsTb₂Cl₇, K₃TbCl₆, Rb₃TbCl₆ and Cs₃TbCl₆ compounds. Both types of compounds, i.e. M₃TbCl₆ and MTb₂Cl₇ (M=K, Rb, Cs) melt congruently and show additionally a solid–solid phase transition with a corresponding enthalpy Δ_trs H ⁰ of 6.1, 7.6 and 7.0 kJ mol^–1 for potassium, rubidium and caesium M₃TbCl₆ compounds andΔ_trs H ⁰ of 17.1 (rubidium) and of 12.1 and 10.9 kJ mol^–1 (caesium) for MTb₂Cl₇ compounds, respectively. The enthalpies of fusion were measured for all the above compounds with the exception of Rb₃TbCl₆ and Cs₃TbCl₆. The heat capacities of the solid and liquid compounds have been determined by differential scanning calorimetry (DSC) in the temperature range 300–1100 K. The experimental heat capacity strongly increases in the vicinity of a phase transition, but varies smoothly in the temperature ranges excluding these transformations. C _p data were fitted by an equation, which provided a satisfactory representation up to the temperatures of C _p discontinuity. The measured heat capacities were checked for consistency by calculating the enthalpy of formation of the liquid phase, which had been previously measured. The results obtained agreed satisfactorily with these experimental data. This revised version was published online in August 2006 with corrections to the Cover Date.     

2-氯-N,N-二甲基尼古丁酰胺的热容和热力学性质研究

Low-temperature heat capacities of 2-chloro-N,N-dimethylnicotinamide were precisely measured with a high-precision automated adiabatic calorimeter over the temperature range from 82 K to 380 K. The compound was observed to melt at （342.15±0.04） K. The molar enthalpy AfusionHm, and entropy of fusion, △fusionSm, as well as the chemical purity of the compound were determined to be （21387±7） J·mol^-1, （62.51±0.01） J·mol^-1·K^-1, （0.9946±0.0005） mass fraction, respectively. The extrapolated melting temperature for the pure compound obtained from fractional melting experiments was （342.25±0.024） K. The thermodynamic function data relative to the reference temperature 298.15 K were calculated based on the heat capacity measurements in the temperature range from 82 to 325 K. The thermal behavior of the compound was also investigated by different scanning calorimetry.     

Thermochemical properties of the Fe-analogue of cryolite, Na3FeF6

Relative enthalpies for low-and high-temperature modifications of Na₃FeF₆ and for the Na₃FeF₆ melt have been measured by drop calorimetry in the temperature range 723–1318 K. Enthalpy of modification transition at 920 K, δ_trans H(Na₃FeF₆, 920 K) = (19 ± 3) kJ mol⁻¹ and enthalpy of fusion at the temperature of fusion 1255 K, δ_fusH(Na₃FeF₆, 1255 K) = (89 ± 3) kJ mol⁻¹ have been determined from the experimental data. Following heat capacities were obtained for the crystalline phases and for the melt, respectively: C _p(Na₃FeF₆, cr, α) = (294 ± 14) J (mol K)⁻¹, for 723 = T/K ≤ 920, C _p(Na₃FeF₆, cr, β) = (300 ± 11) J (mol K)⁻¹ for 920 ≤ T/K = 1233 and C _p(Na₃FeF₆, melt) = (275 ± 22) J (mol K)⁻¹ for 1258 ≤ T/K ≤ 1318. The obtained enthalpies indicate that melting of Na3FeF6 proceeds through a continuous series of temperature dependent equilibrium states, likely associated with the production of a solid solution.      

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.     

Calorimetric study of thermal decomposition of lithium hexafluorophosphate

Enthalpy of formation of lithium hexafluorophosphate was calculated based on the differential scanning calorimetry study of heat capacity and thermal decomposition. It was found that thermal decomposition of LiPF₆ proceeds at normal pressure in the temperature range 450-550 K. Enthalpy of LiPF₆ decomposition is Δ_d H(LiPF₆, c, 298.15 K)= 84.27±1.34 kJ mole^-1. Enthalpy of formation of lithium hexafluorophosphate from elements in standard state is Δ_f H ⁰(LiPF₆,c, 298.15 K) = -2296±3 kJ mol^-1. This revised version was published online in July 2006 with corrections to the Cover Date.     

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.     

The structure and thermochemistry of 3:4,5:6-dibenzo-2-hydroxymethylene-cyclohepta-3,5-dienenone (1) and some related compounds

Condensed and gas phase enthalpies of formation of 3:4,5:6-dibenzo-2-hydroxymethylene-cyclohepta-3,5-dienenone (1, (−199.1 ± 16.4), (−70.5 ± 20.5) kJ mol⁻¹, respectively) and 3,4,6,7-dibenzobicyclo[3.2.1]nona-3,6-dien-2-one (2, (−79.7 ± 22.9), (20.1 ± 23.1) kJ mol⁻¹) are reported. Sublimation enthalpies at T=298.15 K for these compounds were evaluated by combining the fusion enthalpies at T = 298.15 K (1, (12.5 ± 1.8); 2, (5.3 ± 1.7) kJ mol⁻¹) adjusted from DSC measurements at the melting temperature (1, (T _fus, 357.7 K, 16.9 ± 1.3 kJ mol⁻¹)); 2, (T _fus, 383.3 K, 10.9 ± 0.1) kJ mol⁻¹) with the vaporization enthalpies at T = 298.15 K (1, (116.1 ± 12.1); 2, (94.5 ± 2.2) kJ mol⁻¹) measured by correlation-gas chromatography. The vaporization enthalpies of benzoin ((98.5 ± 12.5) kJ mol⁻¹) and 7-heptadecanone ((94.5 ± 1.8) kJ mol⁻¹) at T = 298.15 K and the fusion enthalpy of phenyl salicylate (T _fus, 312.7 K, 18.4 ± 0.5) kJ mol⁻¹) were also determined for the correlations. The crystal structure of 1 was determined by X-ray crystallography. Compound 1 exists entirely in the enol form and resembles the crystal structure found for benzoylacetone.     

Enthalpy of Phase Transitions and Heat Capacity of Stoichiometric Compounds in LaBr3-MBr Systems (M=K,Rb, Cs)

Molar enthalpies of solid-solid and solid-liquid phase transitions of the LaBr₃, K₂LaBr₅, Rb₂LaBr₅, Rb₃LaBr₆ and Cs₃LaBr₆ compounds were determined by differential scanning calorimetry. K₂LaBr₅ and Rb₂LaBr₅ exist at ambient temperature and melt congruently at 875 and 864 K, respectively, with corresponding enthalpies of 81.5 and 77.2 kJ mol^-1. Rb₃LaBr₆ and Cs₃LaBr₆ are the only 3:1 compounds existing in the investigated systems. The first one forms from RbBr and Rb₂LaBr₅ at 700 K with an enthalpy of 44.0 kJ mol^-1 and melts congruently at 940 K with an enthalpy of 46.7 kJ mol^-1. The second one exists at room temperature, undergoes a solid-solid phase transition at 725 K with an enthalpy of 9.0 kJ mol^-1 and melts congruently at 1013 K with an enthalpy of 57.6 kJ mol^-1. Two other compounds existing in the CsBr-based systems (Cs₂LaBr₅ and CsLa₂Br₇) decompose peritectically at 765 and 828 K, respectively. The heat capacities of the above compounds in the solid as well as in the liquid phase were determined by differential scanning calorimetry. A special method - 'step method' developed by SETARAM was applied in these measurements. The heat capacity experimental data were fitted by a polynomial temperature dependence. This revised version was published online in July 2006 with corrections to the Cover Date.     

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.