The incongruent effusion of ZnGa8S13(s)

The chemistry and thermodynamics of vaporization in a Knudsen effusion cell of the phase ZnGa₈S₁₃ was studied in the range 1115–1246 K where the vapor pressure ranged from 0.25 to 10.0 Pa. Samples prepared by sealed-tube methods and characterized by X-ray diffraction were studied by the simultaneous Knudsen and torsion (Volmer) effusion method. ZnGa₈S₁₃(s) effused incongruently in equilibrium with a saturated solid solution (sss) of ZnS in Ga₂S₃, Ga₂S(g), Zn(g), and S₂(g), always on the ZnSGa₂S₃ join. Ga₂S₃(sss) then effused with net loss of ZnS to the vapor until the composition of Ga₂S₃ was reached. Vapor analysis by combining measured rates of mass loss and momentum loss allowed analysis of the vapor and calculation of equilibrium constants of the effusion equations. Thermodynamic treatment by the third-law method yielded the ΔH° (298 K) of ZnGa₈S₁₃(s) with respect to those of ZnS(s) and 4Ga₂S₃(s), − 52 ± 22 kJ mol ^{− 1}.     

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.     

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.     

The cationic polymerization of fluoral—III. Thermodynamics of polymerization in solution

The equilibrium between fluoral in dichloromethane solution and live condensed liquid polyfluoral has been investigated between 22 and 43°C. Equilibrium monomer concentrations gave: ΔH_ac°(298 K) = -50-8 ± 2·3 kJ mol^?1 and ΔS_sc° (298 K) = -142·7 ± 7·4 J K^-1 mol^-1. With the aid of calibration and monomer vaporization data, thermodynamic values for the polymerization of liquid monomer to liquid polymer were also calculated: ΔH_tc° (298 K) = -47 ± 3 kJ mol^-1 and ΔS_1e° (298 K) = -97 ± 10 J K^-1 mol^-1.     

Thermochemistry of hydrogen tungsten bronze phases HxWO3

The enthalpies of formation of two hydrogen tungsten bronze phases H_0.35WO₃ and H_0.18WO₃ have been determined by solution calorimetry. Values obtained for formation from H₂(g) and WO₃(s) at 298.15 K were H_0.35WO₃(s), ?9.6 ± 0.8 kJ mole^?1 and H_0.18WO₃(s), ?4.8 ± 0.6 kJ mole^?1. The stabilities of these phases towards decomposition, disproportionation and oxidation are discussed.     

Vaporization study of the SbBr3 system by the torsion—effusion method

Vapor pressures of solid antimony tribromide were measured by the torsion—effusion technique. The values obtained can be expressed by the equation log P(atm) = (9.3 ± 1.3) ? (4.4 ± 0.5)/T in the temperature range 324–368 K.The standard heat of vaporization was derived by second- and third-law treatment of the data and compared with values reported in the literature. The value ΔH⁰_vap (298 K) = 19.5 ± 0.5 kcal mole^?1 was derived.     

Vapour pressure of α-iodonaphthalene

Using three different techniques, the vapour pressure of α-iodonaphthalene was measured in the temperature range 322–422 K. The pressure equation log P(kPa) = 8.82 ± 0.29 ? (3719 ± 300) /T, was determined. The enthalpy of vaporization change, ΔH⁰₂₉₈ = 69.4 ± 4.0 kJ mole^?1, was determined as the average of the results obtained by second-and third-law treatment of the experimental data. Antoine's constants, A = 6.258, B = 2010 and C = 171, were also derived.     

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.     

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.     

Sublimation enthalpies of the complexes W(CO)6-x(NCCH3)x (x=1,2,3) and Mo(CO)6-x(NCCH3x(x=1,3)

Vapour pressure measurements have been carried out on the complexes W(CO)_it6-x (NCCH₃x(x=1,2,3) and Mo(CO)_it6-x(NCCH₃x(x=1,3) employing the Knudsen effusion technique. The following enthalpies of sublimation, ΔH²⁹⁸_sub(kJ mole^?1), have been determined from vapour pressure data: W(CO)₅(NCCH₃)=98.1±2.0; W(CO) ₄ (NCCH₃)₂=131.0±6.0; W(CO)₃(NCCH₃₃=103.4±6.0; Mo(CO)₅(NCCH₃)=105.8± 5.6; and Mo(CO)₃(NCCH₃)₃=111.3±3.0.     

Kinetics of HD exchange in the reaction of HBF2 with D2

The rate constant for the unusually rapid HD exchange reaction of D₂ with HBF₂ : D₂(g) + HBF₂(g) → DBF₂(g) + HD(g) has been measured (k₂(298K) = (7.42 ± 2.0) × 10^?23 cm³/molecule s). The activation energy for this reaction has been estimated to be 17.8 ± 1.2 kcal/mole. The mechanism probably involves a multicenter orbital interaction between D₂ and HBF₂.     

The fluorobasicities of ReF7 and IF7 as measured by the enthalpy change ΔH°(EF7(g) → EF6+(g) + F−(g))

Iridium hexafluoride oxidizes ReF₆ (via an ReF₆⁺ salt) and at room temperatures IrF₆, ReF₆, ReF₇ and (IrF₅)₄ are each present in the equilibrium mixture. From these and related findings: ΔH°(ReF₆ → ReF₆⁺ + e^?) 1092 ± 27 kj mole^?1(261 ± 6 kcal mole^?1), and thermodynamic data are selected to yield ΔH°(ReF_7(g) → ReF₆⁺_(g) + F^?_(g))=893 ± 33 kj mole^?1(213 ± 8 kcal mole^?1). From observations on the stability of IF₆⁺BF₄^? and the lattice enthalpy evaluation for the salt, ΔH°(IF_7(g) → IF₆⁺_(g) + F^?_(g))= 870 ± 24 kj mole^?1(208 ± 6 kcal mole^?1).     

Vibrational rate enhancement in the reaction OH + H2(ν = 1) → H2O + H

The rate constant for the reaction between OH and vibrationally excited H₂, OH + H₂(ν = 1)→H₂O + H, has been measured directly at 298 K. k₀₁ is found to be (7.5±3)×10^?13 cm³/molecules, corresponding to a vibrational rate enhancement of k₀₁/k₀₀ = (1.2 ± 0.4) × 10².     

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.     

Kinetics of the dissociation and cis-trans isomerization of o,o'-azodioxytoluene (dimeric o-nitrosotoluene)

The dimer-monomer reactions were investigated for the system cis and transo,o'-azodioxytoluene-o-nitrosotoluene in acetonitrile solvent. For the reaction cis dimer-monomer the following thermodynamic and activation parameters have been derived: ΔH°=58.5±2.5 kJ mole^?1, ΔS°=206.2±3.8 J mole^?1 K^?1, ΔH^≠=63.6±3.3 kJ mole^?1, ΔS^≠=6.3±0.3 J mole^?1 K^?1. The corresponding values for the reaction trans dimer-monomer are: ΔH°=45.6±2.1 kJ mole^?1, ΔS°=162.7±7.1 J mole^?1 K^?1, ΔH^≠=80.8±2.9 kj mole^?1, ΔS^≠=-13.4±0.8 mole^?1 K^?1. There is no evidence of a direct cis-trans isomerization (i.e. a reaction not proceeding via the monomer). NMR and various perturbation techniques monitoring the visible absorption of the monomer were employed.     

Temperature dependence of the reaction rate constants for O(3P) atoms with C2H4, C3H6 and NO(M = N2O), determined by a modulation technique

Rate constants for the reaction of O(³P) atoms with C₃H₄, C₃H₆ and NO(M = N₂O) have been measured over the temperature range 300–392°K using a modulation-phase shift technique. The Arrhenius expressions obtained are:C₂H₄, k₂ = 3.37 × 10⁹ exp[?(1270 ± 200)/RT]liter mole^?1 sec^?1,C₃H₆, k₂ = 2.08 × 10⁹ exp[?(0 ± 300)/RT]liter mole^?1 sec^?1,NO(M = N₂O), k₁ = 9.6 × 10⁹ exp[(900 ± 200/RT]liter² mole^?2 sec^?1.These temperature dependencies of k₂ are in good agreement with recent flash photolysis-resonance flourescence measurements, although lower than previous literature values.     

Diffusion coefficient measurement of O*2(1Δg) in ground state O2

The diffusion coefficient of O_*2(¹Δ_g) in O₂(³Σ^?_g) has been measured as a function of pressure, D^* = 0.201 ± 0.005 cm² s^?1 at 1 atmosphere and 298 K.     

Phase equilibria and thermodynamics of the double oxide phase Cu3TiO4

Phase equilibria in the system CuCu₂OTiO₂ were investigated in the temperature range of 1160–1270 K by means of thermogravimetry and measurements of the oxygen partial pressure. The tie lines on the isothermal phase diagram run from the phase Cu₃TiO₄ to CuO, Cu₂O, and TiO₂. The existence of Cu₃TiO₅ and Cu₂TiO₃ could not be confirmed in this temperature range. The phase “Cu₃TiO₄” is only stable above about 1140 K and its composition fluctuates between about Cu₃TiO_4.3 and Cu₃TiO_3.9. The formation of Cu₃TiO_4.3 according to the reaction 1.6 CuO + 0.7 Cu₂O + TiO₂ = Cu₃TiO_4.3 is endothermic: (1160 < T < 1270 K) ΔH° = (7600 ± 450 J-mole^?1; ΔS° = (6.7 ± 0.4) J·K^?1·mole^?1. The standard Gibbs free energy, enthalpy, and entropy of formation of Cu₃TiO_4.3 at 1200 K are ΔG°_f = ?101.39 kJ, ΔH°_f = ?1115.84 kJ, and S°_f = 466.76 J·K^?1. Rather similar values were found for Cu₃TiO_3.9.     

Rate constant for the reaction NH3 + OH → NH2 + H2O over a wide temperature range

The rate constant for the reaction or NH₃ + OH → NH₂ + H₂O has been measured in a high temperature fast flow reactor over the range 294–1075 K k = (5.41 ± 0.86) × 10^-12 exp[?(2120 ± 143) cal mole^?1/RT cm³ molecule^?1 s^?1. This result is compared with literature values and discussed.     

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.