Standard molar enthalpies of formation of some trichloroanilines by rotating-bomb calorimetry

The standard ( p^o =  0.1 MPa) molar enthalpies of formation Δ_fH_m^o, at the temperature 298.15 K, for crystalline 2,3,4-, 2,4,5-, 2,4,6- and 3,4,5-trichloroaniline were derived from the molar enthalpies of combustion Δ_cH_m^oin oxygen using rotating bomb combustion calorimetry. The reaction products were CO₂(g), N₂(g), and HCl · 600H₂O(l). The standard molar enthalpies of sublimation Δ_cr^gH_m^oat T =  298.15 K were measured by Calvet microcalorimetry. The results are as follows: The derived standard molar enthalpies of formation of the gaseous compounds were compared with values estimated by assuming the enthalpy increment for substitution of chlorine in aniline to be the same as for substitution into benzene.     

The standard molar enthalpy of sublimation ofη5-bis-pentamethylcyclopentadienyl iron measured with an electrically calibrated vacuum-drop sublimation microcalorimetric apparatus

A heat-flow Calvet microcalorimeter was adapted for the measurement of sublimation enthalpies by the vacuum-drop method, with samples of masses in the range 1 mg to 5 mg. The electrically calibrated apparatus was tested by determining the enthalpies of sublimation of benzoic acid and ferrocene, at T =  298.15 K. The obtained results, Δ_cr^gH_m^o(C₇H₆O₂)  =  (88.3  ±  0.5)kJ · mol ^− 1and Δ_cr^gH_m^o(C₁₀H₁₀Fe) =  (73.3  ±  0.1)kJ · mol ^− 1, are in excellent agreement with the corresponding values recommended in the literature. Subsequent application of the apparatus to the determination of the enthalpy of sublimation of η⁵-bis-pentamethylcyclopentadyenyl iron, at T =  298.15 K, led to Δ_cr^gH_m^o(C₂₀H₃₀Fe)  =  (96.8  ±  0.6)kJ · mol ^− 1.     

Thermodynamic study on the sublimation of six methylnitrobenzoic acids

The Knudsen mass-loss effusion technique was used to measure the vapour pressures at different temperatures of the following six compounds: 2-methyl-3-nitrobenzoic acid, between T =  357.16 K and T =  371.16 K; 2-methyl-6-nitrobenzoic acid, between T =  355.16 K and T =  369.16 K; 3-methyl-2-nitrobenzoic acid, between T =  371.16 K and T =  385.14 K; 3-methyl-4-nitrobenzoic acid, between T =  363.21 K and T =  379.16 K; 4-methyl-3-nitrobenzoic acid, between T =  363.10 K and T =  377.18 K; 5-methyl-2-nitrobenzoic acid, between T =  355.18 K and T =  371.08 K. From the temperature dependence of the vapour pressure, the standard molar enthalpies of sublimation were derived by the Clausius–Clapeyron equation and the molar entropies of sublimation at equilibrium pressures were calculated. Using estimated values for the heat capacity differences between the gas and the crystal phases of the studied compounds the standard, p^o =  10⁵Pa, molar enthalpies Δ_cr^gH_m^o, entropies Δ_cr^gS_m^oand Gibbs energies Δ_cr^gG_m^oof sublimation at T =  298.15 K, were derived:     

Experimental thermochemical study of the enthalpies of formation and sublimation of isonicotinamide,picolinamide, nicotinamide,isonicotinamideN-oxide,and nicotinamideN-oxide. The dissociation enthalpies of the N–O bonds

The standard (p ^∘  =  0.1MPa) molar enthalpies of combustion in oxygen, at T =  298.15 K, for crystalline picolinamide (2-NH₂COPy), nicotinamide (3-NH₂COPy), isonicotinamide (4-NH₂COPy), nicotinamide N -oxide (3- NH₂COPyNO), and isonicotinamide N - oxide (4-NH₂COPyNO) were measured by static-bomb calorimetry. These values were used to derive the standard molar enthalpies of formation of the crystalline compounds. The standard molar enthalpies of sublimation, at T =  298.15 K, for the three pyridinecarboxamide isomers were measured by microcalorimetry and the standard molar enthalpies of sublimation for the two pyridinecarboxamide N -oxide compounds were measured by a mass-loss effusion technique. From the enthalpies of formation of the gaseous compounds, the molar dissociation enthalpies D_m^oof the (N ⁺ – O ⁻ ) covalent bonds were derived. Comparison has been made with D_m^o(N–O) values in pyridine N -oxide derivatives.     

Thermochemistry of some barium compounds

The molar enthalpies of reaction of metallic barium with 0.047 mol·dm⁻³ HClO₄ as well as the molar enthalpies of dissolution of BaCl₂ in 1.01 mol·dm⁻³ HCl and in water have been measured at T=298.15 K in a sealed swinging calorimeter with an isothermal jacket. From these results the standard molar enthalpy of formation of the barium ion in an aqueous solution at infinite dilution, as well as the enthalpies of formation of barium chloride and barium perchlorate, are calculated to be: Δ_fH⁰_m(Ba²⁺,aq)=−(535.83±1.25) kJ · mol⁻¹; Δ_fH⁰_m(BaCl₂,cr)=−(855.66±1.28) kJ · mol⁻¹; and Δ_fH⁰_m(BaClO₄,cr)=−(796.26±1.35) kJ · mol⁻¹. The results obtained are discussed and compared with previous experimental values.     

A calorimetric study of N,N-diethyl-N′-furoylthiourea and N,N-diisobutyl-N′-furoylthiourea

The standard ( p^o =  0.1 MPa) molar enthalpies of combustion in oxygen, at T =  298.15 K, were measured by rotative bomb calorimetry for crystalline N, N -diethyl- N^′-furoylthiourea, (2-C₄H₃O)CONHCSN(C₂H₅)₂, HFET, and N, N -diisobutyl- N^′-furoylthiourea, (2-C₄H₃O)CONHCSN(iso-C₄H₉)₂, HFIB. The standard molar enthalpies of sublimation of both HFET and HFIB were measured by high-temperature Calvet microcalorimetry. These values were used to derive the standard molar enthalpies of formation of the compounds, in their crystalline and gaseous phases.     

The thermodynamics of formation,molar heat capacity,and thermodynamic functions ofZrTiO4(cr)

As part of an ongoing study of titanate-based ceramic materials for the disposal of surplus weapons-grade plutonium, we report thermodynamic properties of a sample ofzirconium titanate (ZrTiO₄) quenched from a high-temperature synthesis. The standard enthalpy of formationΔ_fH_m^o was obtained by using high-temperature oxide-melt solution calorimetry. The molar heat capacity C_{p, m}was measured fromT =  13 K to T =  400 K in an adiabatic calorimeter and extrapolated toT =  1800 K by using an equation fitted to the low-temperature results. The results atT =  298.15 K areΔ_fH_m^o =  − (2024.1  ±  4.5)kJ · mol ^− 1,Δ₀^TS_m^o =  (116.71  ±  0.31 )J · K ^− 1· mol ^− 1, andΔ_fG_m^o =  − (1915.8  ±  4.5 )kJ · mol ^− 1; the molar entropy includes a contribution of 2 R ln2 to account for the random mixing of Zr^4 + and Ti^4 + on a four-fold crystallographic site. Values for the standard molar Gibbs energies and enthalpies of formation of ZrTiO_4,Δ_fG_m^oandΔ_fH_m^o , and for the free energies and enthalpies for the reaction to form ZrTiO₄(cr) from ZrO₂(cr) and TiO₂(cr), are tabulated over the temperature interval, 0 ⩽(T / K)⩽ 1800. From these results, we conclude that ZrTiO₄is not stable with respect to (ZrO₂ +  TiO₂) at T =  298.15 K, but becomes so at T =  (1250  ±  150) K.     

Thermodynamics of dibenzo-p-dioxin and 1,2,3,4-tetrachlorodibenzo-p-dioxin fromT = 5 K toT = 490 K

In adiabatic low-pressure and dynamic calorimeters the temperature dependence of the standard molar heat capacity C_{p, m}^oof dibenzo- p -dioxin and 1,2,3,4-tetrachlorodibenzo- p -dioxin have been determined at temperatures in the range T =  5 K to T =  490 K: from T =  5 K to T =  340 K with an accuracy of about 0.2 per cent and with an accuracy of 0.5 per cent to 1.5 per cent between T =  340 K and T =  490 K. The temperatures, enthalpies, and entropies of melting of the above compounds have been determined. The experimental data were used to calculate the thermodynamic functions C_{p, m}^o / R, Δ₀^TH_m^o / (R·K), Δ₀^TS_m^o / R, and Φ_m^o = Δ₀^TS_m^o − Δ₀^TH_m^o / T(where R is the universal gas constant) in the range T →  0 to T =  490 K. The isochoric heat capacity C_{V, m}of both dioxins has been estimated over the range T →  0 to T_fus. The effect of substitution of four hydrogen atoms by chlorine atoms on the lattice and atomic components of the isochoric heat capacity was considered.     

Experimental standard molar enthalpies of formation of crystalline 3,5-dimethylpyrazole, 3,5-dimethyl-4-nitrosopyrazole, 1,3,5-trimethyl-4-nitrosopyrazole,and 3,5-dimethyl-1-phenyl-4-nitrosopyrazole

The standard (p^o =  0.1 MPa) molar enthalpies of combustion in oxygen, at T =  298.15 K, for crystalline 3,5-dimethylpyrazole (Me₂Pyr), 3,5-dimethyl-4-nitrosopyrazole (Me₂PyrNO), 1,3,5-trimethyl-4-nitrosopyrazole (Me₃PyrNO), and 3,5-dimethyl-1-phenyl-4-nitrosopyrazole (Me₂PhPyrNO) were measured by static-bomb calorimetry. These values were used to derive the standard molar enthalpies of formation of the crystalline compounds. The standard molar enthalpies of sublimation for these four compounds were measured by microcalorimetry.The experimental results obtained allow us to derive the values of the standard molar enthalpies of formation, in the gaseous state, for the monomeric compounds involved in this work. These last values are discussed comparatively with results previously obtained for some aromatic nitroso derivatives.     

Thermodynamic study on the sublimation of 3-phenylpropionic acid and of three methoxy-substituted 3-phenylpropionic acids

The Knudsen mass-loss effusion technique was used to measure the vapour pressures at different temperatures of the following compounds: 3-phenylpropionic acid, between T =  305.17 K and T =  315.17 K; 3-(2-methoxyphenyl)propionic acid, between T =  331.16 K and T =  347.16 K; 3-(4-methoxyphenyl)propionic acid, between T =  341.19 K and T =  357.15 K; 3-(3,4-dimethoxyphenyl)propionic acid, between T =  352.18 K and T =  366.16 K. From the temperature dependence of the vapour pressure, the standard molar enthalpies of sublimation Δ_cr^gH_m^owere derived by the Clausius–Clapeyron equation and the molar entropies of sublimation at equilibrium pressures were calculated. On the basis of estimated values for the heat capacity differences between the gas and the crystal phases of the studied compounds the standard, p ^∘  =  10⁵Pa, molar enthalpies, entropies and Gibbs energies of sublimation at T =  298.15 K, were derived:     

Temperature and salt addition effects on the solubility behaviour of some phenolic compounds in water

Solubility-temperature dependence data for six phenolic compounds (PhC), contained in olive mill wastewater (OMWW), in water and in some chloride salts (KCl, NaCl, and LiCl) aqueous solutions have been presented and solution standard molar enthalpies (Δ_solH^∘) were determined using Van’t Hoff plots. The temperature was varied from 293.15 K to 318.15 K. Solubility data were estimated using a thermostated reactor and HPLC analysis. It has been observed that solubility, in pure water and in aqueous chloride solutions, increases with increasing temperature. The salting-out LiCl > NaCl > KCl order obtained at 298.15 K is confirmed. Results were interpreted in terms of the salt hydration shells and the ability of the solute to form hydrogen-bond with water. The standard molar Gibbs free energies of transfer of PhC (Δ_trG^∘) from pure water to aqueous solutions of the chloride salts have been calculated from the solubility data. In order to estimate the contribution of enthalpic and entropic terms, standard molar enthalpies (Δ_trH^∘) and entropies (Δ_trS^∘) of transfer have also been calculated. The decrease in solubility is correlated to the positive Δ_trG^∘ value which is mainly of enthalpic origin.     

The enthalpy of dilution and thermodynamics of Na2CO3(aq) and NaHCO3(aq) fromT = 298 K toT = 523.15 K and pressure of 40 MPa

Molar enthalpies of dilution Δ_dilH_mofNa₂CO₃(aq) were measured from molality m =  1.45 mol · kg ^− 1to m =  0.008 mol · kg ^− 1at seven temperatures from T =  298 K toT =  523 K at the pressure p =  7 MPa, and at four temperatures fromT =  371 K to T =  523 K at the pressurep =  40 MPa. Molar enthalpies of dilutionΔ_dilH_m of NaHCO₃(aq) were measured fromm =  0.98 mol · kg ^− 1tom =  0.007 mol · kg ^− 1at the same temperatures and pressures. Hydrolysis and ionization equilibria contribute substantially to the measured enthalpies under many of the conditions of this study. Explicit consideration of these reactions, using thermodynamic quantities from previous studies, facilitates a quantitative representation of apparent molar enthalpies, activity coefficients, and osmotic coefficients with the Pitzer ion-interaction treatment over the ranges of temperature, pressure, and molality of the experiments.     

The excess molar enthalpies of (N-methyl-2-pyrrolidinone + mono-, or di-, or trichlorobenzene) atT = 298.15 K

Excess molar enthalpies H_m^EatT =  298.15 K are reported for (N -methyl-2-pyrrolidinone  +  chlorobenzene, or 1,2-dichlorobenzene, or 1,3-dichlorobenzene, or 1,2,4,-trichlorobenzene). The values ofH_m^E were obtained by using the flow calorimetric method. All the mixtures, over the whole composition range, are formed exothermically. The H_m^Eresults are discussed in terms of the NRTL and UNIQUAC models.     

Thermodynamics of vaporization of some alkyladamantanes

The boiling temperature of 1,3-dimethyladamantane was measured by comparative ebulliometry over the pressure range 6  <  (p / kPa)  <  100. The temperature dependencies of saturation vapour pressure and enthalpy of vaporization, and the normal boiling temperature,T_b =  476.53 K, were derived. The enthalpy of vaporization,ΔlgHmo =  (49.21  ±  0.2)kJ · mol ^− 1, was calorimetrically measured atT =  308.15 K. The experimental and calculatedΔlgHmo values were found to agree within the error limits. Densities of the liquid phase were measured at the temperatures (293.15, 298.15, and 303.15) K. The experimental vapour pressures of 1,3-dimethyladamantane and of the previously studied 1,3,5-trimethyladamantane were extrapolated to the regions of the liquid phases from the triple to the critical temperatures.     

Study on the enthalpy of solution and enthalpy of dilution for the ionic liquid [C3mim][Val] (1-propyl-3-methylimidazolium valine)

A new amino acid ionic liquid (AAIL) [C₃mim][Val] (1-propyl-3-methylimidazolium valine) was prepared by the neutralization method. Using the solution-reaction isoperibol calorimeter, molar solution enthalpies of the ionic liquid [C₃mim][Val] with known amounts of water and with different concentrations in molality were measured at T = 298.15 K. In terms of standard addition method (SAM) and Archer’s method, the standard molar enthalpy of solution for [C₃mim][Val] without water, ${\mathrm{\Delta }}_{\text{s}}{H}_{\text{m}}^{\circ }$ = (−55.7 ± 0.4) kJ · mol⁻¹, was obtained. The hydration enthalpy of the cation [C₃mim]⁺, ΔH₊ ([C₃mim]⁺) = −226 kJ · mol⁻¹, was estimated in terms of Glasser’s theory. Using the RD496-III heat conduction microcalorimeter, the molar enthalpies of dilution, Δ_DH_m(m_i → m_f), of aqueous [C₃mim][Val] with various values of molality were measured. The values of Δ_DH_m(m_i → m_f) were fitted to Pitzer’s ion-interaction model and the values of apparent relative molar enthalpy, ^φL, calculated using Pitzer’s ion-interaction model.     

Thermodynamic properties of tetraphenylphosphonium perchlorate and tetraphenylarsonium perchlorate fromT → 0 toT = 340 K

The temperature dependence of the standard molar heat capacity C_{p, m}^oof samples of crystalline tetraphenylphosphonium perchlorate and tetraphenylarsonium perchlorate was measured in an adiabatic low-pressure calorimeter between T =  4.8 K and T =  340 K and from T =  5.8 K to T =  340 K, respectively, mostly to within a precision of 0.2 per cent. For tetraphenylphosphonium perchlorate, an anomalous change of the heat capacity in the range T =  125 K to T =  185 K, probably arising from the excitation of hindered rotations of atomic groups, was found and its thermodynamic characteristics were determined. No such anomaly was observed for tetraphenylarsonium perchlorate. The data obtained were used to calculate the thermodynamic functions C_{p, m}^o(T) / R, Δ₀^TH_m^o / R·K, Δ₀^TS_m^o / R, and Φ_m^o = Δ₀^TS_m^o − Δ₀^TH_m^o / T(where R is the universal gas constant) of the compounds between T →  0 and T =  340 K.     

The solubility measurements of sodium dicarboxylate salts; sodium oxalate,malonate, succinate,glutarate, and adipate in water from T = (279.15 to 358.15) K

The solubility measurements of sodium dicarboxylate salts; sodium oxalate, malonate, succinate, glutarate, and adipate in water at temperatures from (278.15 to 358.15 K) were determined. The molar enthalpies of solution at T = 298.15 K were derived: Δ_solH_m (m = 2.11 mol · kg^?1) = 13.86 kJ · mol^?1 for sodium oxalate; Δ_solH_m (m = 3.99 mol · kg^?1) = 14.83 kJ · mol^?1 for sodium malonate; Δ_solH_m (m = 2.45 mol · kg^?1) = 14.83 kJ · mol^?1 for sodium succinate; Δ_solH_m (m = 4.53 mol · kg^?1) = 16.55 kJ · mol^?1 for sodium glutarate, and Δ_solH_m (m = 3.52 mol · kg^?1) = 15.70 kJ · mol^?1 for sodium adipate. The solubility value exhibits a prominent odd–even effect with respect to terms with odd number of sodium dicarboxylate carbon numbers showing much higher solubility. This odd–even effect may have implications for the relative abundance of these compounds in industrial applications and also in the atmospheric aerosols.     

Solubilities of l-glutamic acid, 3-nitrobenzoic acid,p-toluic acid,calcium-l-lactate,calcium gluconate,magnesium-dl-aspartate,and magnesium-l-lactate in water

Solubilities of l -glutamic acid, 3-nitrobenzoic acid, p -toluic acid, calcium-l -lactate, calcium gluconate, magnesium- dl -aspartate, and magnesium- l -lactate in water were determined in the temperature range 278 K to 343 K. The apparent molar enthalpies of solution at T =  298.15 K as derived from these solubilities areΔ_solH_m (l -glutamic acid,m_sat =  0.0565 mol · kg ^− 1)  =  30.2 kJ · mol ^− 1,Δ_solH_m (3-nitrobenzoic acid, m =  0.0188 mol · kg ^− 1)  =  28.1 kJ · mol ^− 1, Δ_solH_m( p - toluic acid, m =  0.00267 mol · kg ^− 1)  =  23.9 kJ · mol ^− 1,Δ_solH_m (calcium- l -lactate tetrahydrate,m =  0.2902 mol · kg ^− 1)  =  25.8 kJ · mol ^− 1,Δ_solH_m (calcium gluconate, m =  0.0806 mol · kg ^− 1)  =  22.1 kJ · mol ^− 1, Δ_solH_m(magnesium-dl -aspartate tetrahydrate, m =  0.1469 mol · kg ^− 1)  =  11.5 kJ · mol ^− 1, andΔ_solH_m (magnesium- l -lactate trihydrate,m =  0.3462 mol · kg ^− 1)  =  3.81 kJ · mol ^− 1.     

Combined experimental and computational thermochemistry of isomers of chloronitroanilines

The standard (p^° = 0.1 MPa) molar enthalpies of formation, at T = 298.15 K, of 4-chloro-3-nitroaniline and 5-chloro-2-nitroaniline, in the condensed phase, were derived from their standard molar energies of combustion, in oxygen, to yield CO₂(g), N₂(g), and HCl · 600H₂O(l), measured by rotating bomb combustion calorimetry. From the temperature dependence of the vapour pressures of these compounds, measured by the Knudsen effusion technique, their standard molar enthalpies of sublimation, at T = 298.15 K, were derived by means of the Clausius–Clapeyron equation. The Calvet microcalorimetry was also used to measure the standard molar enthalpies of sublimation of these compounds, at T = 298.15 K. The combination of the standard molar enthalpies of formation in the condensed phases and the standard molar enthalpies of sublimation yielded the standard molar enthalpies of formation in the gaseous phase at T = 298.15 K for each isomer. Further, the standard (p^° = 0.1 MPa) molar enthalpies, entropies and Gibbs free energies of sublimation, at T = 298.15 K, were also derived.The standard molar enthalpies of formation, in the gaseous phase of all the chloronitroaniline isomers were also estimated by the Cox scheme and by the use of computational thermochemistry and compared with the available experimental values.     

The vapour pressures of saturated aqueous solutions of magnesium,calcium, nickel and zinc acetates and molar enthalpies of solution of magnesium,calcium, zinc and lead acetates

Vapour pressures of water over saturated solutions of magnesium, calcium, nickel and zinc acetates were determined as a function of temperature. The vapour pressures served to evaluate the water activities, osmotic coefficients and molar enthalpies of vaporization. Molar enthalpies of solution of magnesium acetate tetrahydrate,Δ_solH_m (T =  294.71K ;m =  0.01 mol · kg ^− 1)  =  − (15.65  ±  0.97)kJ · mol ^− 1; calcium acetate,Δ_solH_m (T =  297.18K ;m =  0.01 mol · kg ^− 1)  =  − (28.15  ±  0.28)kJ · mol ^− 1; zinc acetate dihydrate,Δ_solH_m (T =  297.36K ;m =  0.01 mol · kg ^− 1)  =  − (22.49  ±  0.90)kJ · mol ^− 1and lead acetate trihydrate,Δ_solH_m (T =  297.36K ;m =  0.0086 mol · kg ^− 1)  =  (22.46  ±  0.94)kJ · mol ^− 1, were determined calorimetrically.