Thermal decomposition of zinc and cadmium zirconyl oxalates

The enthalpy of formation at 298.15 K of the polymer Al₁₃O₄(OH)₂₈(H₂O)³⁺₈ and an amorphous aluminium trihydroxide gel was studied using an original differential calorimetric method, already developed for adsorption experiments, and aluminium-27 NMR spectroscopy data. ΔH_f “Al₁₃” (298.15 K) = ? 602 ± 60.2 kJ mole^?1 and ΔH_f Al(OH)₃ (298.15 K) = ? 51 ± 5 kJ mole^?1. Using theoretical values of ΔG_R “Al₁₃” and ΔG_R Al(OH)₃, we calculated ΔG_f “Al₁₃” (298.15 K) = ? 13282 kJ mole^?1; ΔS_f “Al₁₃” (298.15 K) = + 42.2 kJ mole^?1; ΔG_f Al(OH)₃ (298.15 K) = ? 782.5 kJ mole^?1; and ΔS_f Al(OH)₃ (298.15 K) = + 2.4 kJ mole^?1.     

Thermodynamique de substances azotees. IX. Etude thermochimique de la benzamide. Comparaison des grandeurs energetiques liees a la structure de quelques amides et thioamides

The enthalpy of sublimation of benzamide was obtained by calorimetry in the range 323<T (K)<350. From values of ΔH_sub(T)=f(T), it was possible to determine ΔH⁰_sub (298.15 K)=101.7±1.0 kJ mole^?1. Using previous data on ΔH⁰_f (c, 298.15 K) obtained by combustion calorimetry, the value of ΔH⁰_f (g, 298.15 K)=?100.9±1.2 kJ mole^?1 was calculated. With the use of energetical values concerning thioacetamide, thiobenzamide and thiourea, on the one hand, and acetamide, benzamide and urea, on the other, a comparative study was made.     

Thermodynamics of redox reactions involving nicotinamide adenine dinucleotide

Literature data on the thermodynamics of redox nicotinamide adenine dinucleotide (NAD) dependent reactions have been analyzed. It has been established that for the redox reaction of NAD

where all substances except H₂ are in the aqueous buffer with the ionization enthalpy equal to zero, the most reliable thermodynamic parameters should be considered as: ΔH(298.15 K; pH 7)=?27.4±1.7 kJ mole^?1; ΔG (298.15K; pH 7)=±17.8 kJ mole^?1. From the above thermodynamic parameters of the reaction ΔH, ΔG and ΔS for reactions of NAD with natural substrates, synthetic mediators and some inorganic compounds have been calculated.     

The heat of dehydration of concentrated sodium chloride and potassium chloride solutions

The molar heats of dehydration, ΔH¯_dehyd., of concentrated sodium chloride and potassium chloride solutions were measured with a differential scanning calorimeter in the scanning and isothermal modes. The overall ΔH¯_dehyd. was found to be 44.5 and 44.3 kJ mole^?1 H₂O for NaCl and KCl solutions respectively. There is an astonishing difference between concentrated NaCl and KCl solutions in the way water is lost. The number of fractions of heat dehydration were 2 for NaCl and 3 for KCl. The excess ΔH¯_dehyd. was about 10 kJ mole^?1 H₂O for fraction II of NaCl, and 17 and 55 kJ mole^?1 H₂O for fractions II and III, respectively, of KCl.     

Thermodynamique de composes azotes. VII. Etude thermochimique du pyrazole et de l'imidazole

Enthalpies of sublimation for pyrazole and imidazole have been obtained by calorimetry at 298.15K. The ΔH⁰_sub (298.15 K) values for these two compounds are, respectively, 69.16 ± 0.32 and 74.50 ± 0.40 kJ mole^?1. From literature data obtained by combustion calorimetry for ΔH⁰_f (c, 298.15 K), the enthalpies of formation of these compounds in the gaseous state (pyrazole: 185.1 ± 2.3 kJ mole^?, imidazole: 133.0 ± 1.7 kJ mole^?1) have been derived. Several energy values related to the molecular structure of these two compounds (as resonance energy, enthalpy of isomerization, …) have been determined. The study of pyrazole has enabled us to contribute to the evaluation of some characteristics of the NN bond.     

Equilibrium sublimation and thermodynamic properties of SnS

Knudsen effusion studies of the sublimation of polycrystalline SnS, prepared by annealing and chemical vapor transport, have been performed employing vacuum micro-balance techniques in the temperature range 733–944 K and at pressures ranging from about 6 × 10^?3 to 11 Pa.The third-law heats of sublimation and second-law entropy of reaction SnS(s) = SnS(g) were determined to be ΔH⁰₂₉₈ = 220.4 ± 3.0 kJ mole^? and ΔS⁰₂₉₈ = 162.4 ± 4.5 J K^?1 mole^?1. From these data the standard heat of formation and absolute entropy of SnS(s) were calculated to be ?102.9 ± 4.0 kJ mole^?1 and 79.9 ± 6.0 J K^?1, respectively.     

Vaporization chemistry and thermodynamics in the CdGa2S4-Ga2S3 system

The chemistry and thermodynamics of vaporization of CdGa₂S₄(s), CdGa₈S₁₃(s), and Ga₂S₃(s) were studied by computer-automated, simultaneous Knudsen-effusion and torsion-effusion, vapor pressure measurements in the temperature range 967–1280 K. The vaporization was incongruent with loss of Cd(g) + 1/2 S₂(g) and production of CdGa₈S₁₃(s), a previously unknown compound, in equilibrium with CdGa₂S₄(s), until the solid became CdGa₈S₁₃ only. Then, incongruent vaporization continued with production of Ga₂S₃(s) until the solid was Ga₂S₃ only. The latter vaporized congruently. The ΔH°(298 K) of combination of one mole of CdS(s) with one mole of Ga₂S₃(s) to give CdGa₂S₄(s) was ?22.6 ± 0.9 kJ mole^?1. The 2H2(298 K) of combination of one mole of CdS(s) with four moles of Ga₂S₃(s) to give CdGa₈S₁₃(s) was ?25.5 ± 1.1 kJ mole^?1. The 2H2(298K) of CdGa₈S₁₃(s) with respect to disproportionation into CdGa₂S₄(s) and 3 Ga₂S₃(s) was ?2.8 ± 0.6 kJ mole^?1. CdGa₈S₁₃(s) was not observed at room temperature. The 2H2(298 K) of vaporization of the residual Ga₂S₃(s) was 663.4 ± 0.8 kJ mole^?1, which compared well with a value of 661.4 ± 0.3 kJ mole^?1 already available from the literature. Implications of small variations in stoichiometry of compounds in this study were observed and are discussed.     

Thermodynamic properties of alloys of the Al-Co and Al-Co-Sc systems

Enthalpies of mixing for melts of the binary Al-Co system at 1870 K in the range 0 < x _Co < 0.25, and at 1620 K, 0 < x _Co < 0.12, are investigated by means of isoperibolic calorimetry. Enthalpies of mixing for melts of the ternary Al-Co-Sc system are investigated at 1870 K for sections Al_{0.75(1 ? x)}Co_{0.25(1 ? x)}Sc _x , 0 < x < 0.024, and Al_{0.88(1 ? x)}Co_{0.12(1 ? x)}Sc _x , 0 < x < 0.044. Using the literature data on the enthalpies of mixing for liquid and solid alloys, the activities of melt components, and the phase diagram of the Al-Co system, the thermodynamic properties of liquid and solid alloys of the Al-Co system over a wide range of temperatures and compositions are calculated using a software package of our own design, based on the model of ideal associated solutions (IAS). The enthalpies of mixing and the liquidus surface of the phase diagram of the ternary Al-Co-Sc system over the interval of concentrations are estimated by modeling with data on binary boundary subsystems. All of the components of both the binary Al-Co and ternary Al-Co-Sc systems tend to interact with one another quite strongly: ΔH _min(Al-Co) = ?32.5 kJ/mol at x _Co = 0.44; ΔH _min(Al-Co-Sc) = ?46 kJ/mol for Al_0.4Co_0.3Sc_0.3 (estimated).     

Vapor pressure measurements of ferrocene,mono- and 1,1′-di-acetyl ferrocene

By using different techniques the vapor pressure of ferrocene, mono-acetyl ferrocene and 1,1′-di-acetyl ferrocene was measured. The following pressure—temperature equations were derived ferrocene log P(kPa)= 9.78 ± 0.14 ? (3805 ± 46)/T mono-acetyl ferrocene log P(kPa) = 14.83 ± 0.14 ? (5916 ± 48)/T 1,1′-di-acetyl ferrocene log P(kPa) = 8.82 ± 0.11 ? (4289 ± 44)/T By second- and third-law treatment of the vapor data the ΔH⁰_sub,298 = 74.0 ± 2.0 kJ mole^?1 for the sublimation process of ferrocene was calculated and compared with the literature data. For the sublimation enthalpy of mono- and 1,1′-di-acetyl ferrocene the values ΔH⁰_sub,298 = 115.6 ± 2.5 kJ mole^?1 and ΔH⁰_sub,298 = 91.9 ± 2.5 kJ mole^?1 were derived by second-law treatment. Thermal functions of these compounds were also estimated.     

Zur Thermochemie der Verbindung Ba(NO3)2·2 KNO3

From the heats of solution for Ba(NO₃)₂ (c), KNO₃ (c; II), and Ba(NO₃)₂ · 2 KNO₃ (c) the heat of combination of the double salt from its component salts ΔH ₂₉₈ ⁰ =(?2.168±0.028) kcal · mole^?1 and the standard heat of formation ΔH _f,298 ⁰ =?474.75 kcal · mole^?1 have been determined. The values of derived thermodynamic properties are summarized in table 4.     

Bildungsenthalpie von Uranpentachlorid

The standard enthalpy of formation of UCl₅ has been determined as ΔH _f ^,298/0 UCl₅ (s)=?247.7±0.5 kcal/mol (?1036.4±2.1 kJ/mol) by reacting uranium with chlorine gas in the presence of excess liquid chlorine at 298° K.     

Thermodynamic study of the vaporization of uracil

The vapour pressure of uracil was measured in the temperature range 452–587 K using different techniques and the pressure—temperature equation log P(kPa) = 12.13 ± 0.50 — (6823 ± 210)/T was derived. The thermodynamic functions of gaseous and solid uracil were also evaluated through spectroscopic and calorimetric measurements. The sublimation enthalpy of uracil, ΔH⁰₂₉₈ = 131 ± 5 kJ mole^?1, was derived from second and third law treatment of the vapour data.     

The heat of dehydration of halophilic bacteria as measured by differential scanning calorimetry (DSC)

The heat of dehydration of two species of halophilic bacteria and of red cell pellets was measured by DSC. The molar heat of dehydration of H. marismortui was found to be 50.4 kJ mole^?1 H₂O, whereas that of H. halobium was 46.2 kJ mole^?1 H₂O, and that of human red blood cell 40.6 kJ mole^?1 H₂O. The molar heat of dehydration of H. marismortui has been shown to be composed of three fractions; the second one has a molar heat of 58 kJ mole^?1 H₂O and the third one 108 kJ mole^?1 H₂O.     

Zur Kenntnis der Phase BaO · Al2O3 · 7 H2O

On the Compound BaO · Al₂O₃ · 7 H₂O On the basis of investigations using ²⁷Al, ¹H NMR, IR and thermoanalytical methods for the compound BaO · Al₂O₃ · 7 H₂O a constitution as Ba_n[Al₂(OH)₈]_n · 3n H₂O with condensed AlO₆ groups, sharing edges, is proposed. Relations between the Ba/Al ratio and the constitution of anions of barium aluminate hydrates are discussed.     

Thermodynamic properties of benzoylferrocene and 1,1′-dibenzoylferrocene

The vapor pressures of benzoylferrocene and 1,1′-dibenzoylferrocene were measured by torsion-effusion technique. The following pressure-temperature equations were derived benzoylferrocene log P(kPa) = 10.75±0.22?(5314±82)/T 1,1′-dibenzoylferrocene log P(kPa) = 9.29±0.24?(4898±91 )/T Second-law treatment of the experimental data yielded the sublimation enthalpies for benzoylferrocene and 1,1′-dibenzoylferrocene: ΔH⁰_sub,298 = 116.3±6.0 kJ mole^?1 and ΔH⁰_sub,298 = 109.3±6.0 kJ mole^?1 respectively. Thermal functions of these compounds were also estimated.     

Thermodynamic functions and structure of gallium + tellurium liquid alloys

In the frame of our systematic investigation on strongly interacting alloy systems, we have measured the molar enthalpy of formation, ΔH_f, of liquid Ga + Te alloy at 1200 and 1238 K by direct reaction calorimetry, using a Calvet microcalorimeter. The enthalpy of formation, with reference to the pure liquid components, is negative over the whole range of mole fractions x and has a minimum at x_Te ≈ 0.6. ΔH_f(l, x_Te = 0.61, 1200 K) = ?(38.8 ± 0.8) kJ mol^?1. This is evidence for strong chemical interactions in the liquid phase with formation of Ga₂Te₃ clusters. No significant difference was noted between the enthalpies at 1200 and 1238 K. Comparison of the molar integral enthalpies and entropies of formation of liquid Me_0.4^IIITe_0.6 alloys (Me^III  Al, Ga, In, and Tl) shows that the stability of the Me₂Te₃ clusters decreases in the series Al > Ga > In > Tl.     

High temperature Knudsen cell mass spectrometric determination of the heats of atomization of AlAu2 and Al2Au

The atomization energies, ΔH⁰_at,0 of the molecules, AlAu₂ and Al₂ and Al₂Au have been determined as 121 ± 6 and 110 ± 5 kcal mole^?1 or 506.3 ± 25.1 and 460.2 ± 20.9 kJ mole^?1, respectively.Theses atomization energies are discussed in terms of bond strengths and the Pauling model of a polar bond. Available information suggests that AlAu₂ has the structure AuAlAu, but that Al₂Au has the structure AlAlAu. For both molecules divalent gold is shown to be unlikely.     

Tribochemistry and kinetics of Al2(SO4)3·xH2O decomposition

The thermal decomposition of tribochemically activated Al₂(SO₄)₃·xH₂O was studied by TG, DTA and EMF methods. For some of the intermediate solids, X-ray diffraction and IR-spectroscopy were applied to learn more about the reaction mechanism. Thermal and EMF studies confirmed that, even after mechanical activation of Al₂(SO₄)₃·xH₂O, Al₂O(SO₄)₂ is formed as an intermediate. Isothermal kinetic experiments demonstrated that the thermochemical sulphurization of inactivated Al₂(SO₄)₃·xH₂O has an activation energy of 102.2 kJ·mol^?1 in the temperature range 850–890 K. The activation energy for activated Al₂(SO₄)₃·xH₂O in the range 850–890 K is 55.0 kJ·mol^?1. The time of thermal decomposition is almost halved when Al₂(SO₄)₃·xH₂O is activated mechanically. The results permit conclusions concerning the efficiency of the tribochemical activation of Al₂(SO₄)₃·xH₂O and the chemical and kinetic mechanisms of the desulphurization process.     

Enthalpy of the formation of natural hydrous aluminum hydroxosulfate (aluminite)

A thermochemical study of natural aluminum hydroxosulfate Al₂[(OH)₄SO₄] · 7H₂O, aluminite (Nakhodka deposit, West Chukotka, Russia) is performed on a Tian-Calvet “Setaram” high-temperature heat-conducting microcalorimeter (France). The enthalpy of aluminite formation from simple compounds is obtained via the melt calorimetry of dissolution, Δ_f H ^○(298.15 K) = ?4986 ± 21 kJ/mol.     

Kinetic parameters and solid state mechanism of the thermal dehydration of trans[CrF(H2O)(aa′)2]K[Cr(CN)6]H2O And trans[CrF(H2O)(aa′)2]K[CrNO(CN)5]H2O (aa′=ethylenediamine or 1,3-diaminopropane)

The solid phase thermal deaquation of trans[CrF(H₂O)(aa′)₂]K[Cr(CN)₆]H₂O and trans[CrF(H₂O)(aa′)₂]K[CrNO(CN)₅]H₂O (aa′=ethylenediamine or 1,3-diaminopropane) has been investigated by means of TG measurements. The kinetic parameters (activation energy, E_a, activation entropy, ΔS^#, and frequency factor, k₀) have been determined by comparison of the isothermal and non-isothermal studies for all the principal g(α) expressions. The values found for the activation energy are low (between 80 and 110 kJ mole^?1, approximately) and permit the assignment of the deaquation-anation mechanism of the S_N1 type, involving square-pyramid activated complex and elimination of water as Frenkel defects.