Vapour pressure of diethyl phthalate

Measurements of vapour pressure in the liquid phase and of enthalpy of vaporisation and results of calculation of ideal-gas properties for diethyl phthalate are reported. The method of comparative ebulliometry, the static method, and the Knudsen mass-loss effusion method were employed to determine the vapour pressure. A Calvet-type differential microcalorimeter was used to measure the enthalpy of vaporisation. Simultaneous correlation of vapour pressure, of enthalpy of vaporisation and of difference in heat capacities of ideal gas and liquid/solid phases was used to generate parameters of the Cox equation that cover both the (vapour + solid) equilibrium (approximate temperature range from 220 K to 270 K) and (vapour + liquid) equilibrium (from 270 K to 520 K). Vapour pressure and enthalpy of vaporisation derived from the fit are reported at the triple-point temperature T = 269.92 K (p = 0.0029 Pa, Δ_vapH_m = 85.10 kJ · mol⁻¹ ), at T = 298.15 K (p = 0.099 Pa, Δ_vapH_m = 82.09 kJ · mol⁻¹), and at the normal boiling temperature T = 570.50 K (Δ_vapH_m = 56.49 kJ · mol⁻¹). Measured vapour pressures and measured and calculated enthalpies of vaporisation are compared with literature data.     

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:     

Vapor pressures and vaporization enthalpy of codlemone by correlation gas chromatography

The vapor pressure and vaporization enthalpy of codlemone (trans, trans 8,10-dodecadien-1-ol), the female sex hormone of the codling moth is evaluated by correlation gas chromatography using a series of saturated primary alcohols as standards. A vaporization enthalpy of (92.3 ± 2.6) kJ · mol⁻¹ and a vapor pressure, p/Pa = (0.083 ± 0.012) were evaluated at T = 298.15 K. An equation for the evaluation of vapor pressure from ambient temperature to boiling has been derived by correlation for codlemone. The calculated boiling temperature of T_B = 389 K at p = 267 Pa is within the temperature range reported in the literature. A normal boiling temperature of T_B = (549.1 ± 0.1) K is also estimated by extrapolation.     

Vapour pressures of n-pentane determined by comparative ebulliometry

The vapour pressures of n-pentane have been measured using comparative ebulliometry with water as the reference substance. The measurements cover the temperature and pressure ranges 309 K and 102 kPa to 456 K and 2728 kPa. When combined with selected literature results, the range was extended downwards to a temperature and pressure of 268.8 K and 19.9 kPa and the combined data sets were correlated by a Wagner-type equation with a standard deviation of 18 Pa in the vapour pressure. The critical pressure was treated as an adjustable parameter and the value p_c = 3367.4 kPa was obtained using a selected critical temperature, T_c = 469.7 K. The calculated normal boiling temperature was T_b = 309.207 K and an extrapolation to the triple point temperature T_tp = 143.48 K predicted a pressure of p_tp = 0.078 Pa.     

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:     

High pressure phase equilibria in the system 1,1,1,2-tetrafluoroethane + heptylbenzene

Vapour–liquid, liquid–liquid and liquid–liquid–vapour equilibria for the system 1,1,1,2-tetrafluoroethane + heptylbenzene were determined in the temperature range from 260 to 400 K and at pressures up to 12 MPa. The system was found to be a type II system according to the classification of Van Konynenburg and Scott. The (l₂=l₁)g critical endpoint was found at T=320.07 K and P=1.155 MPa. The mole fraction of heptylbenzene in the critical liquid phase in the critical endpoint is approximately 0.20.     

Isothermal (vapour + liquid) equilibrium at several temperatures of (1-chlorobutane + 1-butanol,or 2-methyl-2-propanol)

Vapour pressures of (1-chlorobutane  +  1-butanol, or 2-methyl-2-propanol) at several temperatures between T =  278.15 and T =  323.15 K were measured by a static method. Reduction of the vapour pressures to obtain activity coefficients and excess molar Gibbs energies was carried out by fitting the vapour pressure data to the Redlich–Kister equation according to Barker’s method. For (1-chlorobutane  +  2-methyl-2-propanol) azeotropic mixtures with a minimum boiling temperature were observed over the whole temperature range.     

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.     

Experimental and computational thermodynamic study of ortho-, meta-, and para-methylbenzamide

The Knudsen mass-loss effusion technique was used to measure the vapour pressures of the three crystalline isomers of methylbenzamide. From the temperature dependence of the vapour pressures, the standard molar enthalpies of sublimation and the enthalpies of the intermolecular hydrogen bonds N−H⋯O were calculated. The temperature and molar enthalpy of fusion of the studied isomers were measured using differential scanning calorimetry. The values of the standard (p^° = 0.1 MPa) molar enthalpy of formation in the crystalline phase, at T = 298.15 K, of the compounds studied were derived from their standard massic energies of combustion measured by static-bomb combustion calorimetry. From the experimental values, the standard molar enthalpies of formation in the gaseous phase, at T = 298.15 K, were calculated and compared with the values estimated by employing computational calculations that were conducted using different quantum chemical methods: G3(MP2), G3, and CBS-QB3. Good agreement between experimental and theoretical results is verified. The aromaticity of the compounds has been evaluated through nucleus independent chemical shifts (NICS) calculations.     

Thermodynamic study on the sublimation of 1,2-diphenylethane and of 3-phenylpropiolic acid

The Knudsen mass-loss effusion technique was used to measure the vapour pressures at different temperatures of the following crystalline compounds: 1,2-diphenylethane (bibenzyl), between T =  289.16 K and T =  303.20 K, and of 3-phenylpropiolic acid between T =  329.15 K and T =  343.15 K. From the temperature dependence of the vapour pressure, the standard molar enthalpies of sublimation at the mean temperature of the experimental range were derived by the Clausius–Clapeyron equation. From these results the standard, p^o =  10⁵Pa, molar enthalpies, entropies, and Gibbs energies of sublimation at T =  298.15 K, were calculated:     

Thermodynamic study of phase transitions in methyl esters of ortho- meta- and para-aminobenzoic acids

A static method based on capacitance gauges was used to measure the vapor pressures of the condensed phases of the methyl esters of the three aminobenzoic acids. For methyl o-aminobenzoate the vapor pressures of the liquid phase were measured in the range (285.4 to 369.5) K. For the meta and para isomers vapor pressures of both crystalline and liquid phases were measured in the ranges (308.9 to 376.6) K, and (332.9 to 428.0) K, respectively. Vapor pressures of the latter compound were also measured using the Knudsen effusion method in the temperature range (319.1 to 341.2) K.From the dependence of the vapor pressures on the temperature, the standard molar enthalpies and entropies of sublimation and of vaporization were derived. Differential scanning calorimetry was used to measure the temperatures and molar enthalpies of fusion of the three isomers. The results enabled the estimation of the enthalpy of the intermolecular (N−H^…O) hydrogen bond in the crystalline methyl p-aminobenzoate. A correlation relating the temperature of fusion and the enthalpy and Gibbs energy of sublimation of benzene, methyl benzoates and benzoic acids was derived.     

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.     

Thermodynamic properties of sublimation of the ortho and meta isomers of acetoxy and acetamido benzoic acids

This paper reports vapour pressures measured at several different temperatures using the Knudsen effusion method of ortho-acetoxybenzoic acid (aspirin) (341.1 to 361.1) K, meta-acetoxybenzoic acid (344.2 to 362.2) K, ortho-acetamidobenzoic acid (367.2 to 389.2) K, and meta-acetamidobenzoic acid (423.2 to 441.1) K. The experimental results enabled the determination of the standard molar enthalpies, entropies and Gibbs energies of sublimation, at T = 298.15 K, of the four compounds studied. DSC experiments yield results of the temperature and enthalpy of fusion. The experimental results were compared with literature ones for the para isomers of the acids acetoxybenzoic and acetamidobenzoic. Correlations involving temperature of fusion, and standard molar enthalpy and Gibbs energy of sublimation of several substituted benzoic acids were proposed. Those correlation equations allow a good estimative of volatility of benzoic acid derivatives from their enthalpies of sublimation and temperatures of fusion.     

Vapour pressure and enthalpy of vaporization of aliphatic dialkyl carbonates

Molar enthalpies of vaporization of aliphatic alkyl carbonates: dimethyl carbonate [616-38-6], diethyl carbonate [105-58-8], di-n-propyl carbonate [623-96-1], di-n-butyl carbonate [542-52-9], and dibenzyl carbonate [3459-92-5] were obtained from the temperature dependence of the vapour pressure measured by the transpiration method. A large number of the primary experimental results on temperature dependences of vapour pressures have been collected from the literature and have been treated uniformly in order to derive vaporization enthalpies of dialkyl carbonates at the reference temperature 298.15 K. An internal consistency check was performed on enthalpy of vaporization values for dialkyl carbonates studied in this work.     

Standard molar enthalpy of formation of 1-benzosuberone: An experimental and computational study

The energetics of 1-benzosuberone was studied by a combination of calorimetric techniques and computational calculations.The standard (p° = 0.1 MPa) molar enthalpy of formation of 1-benzosuberone, in the liquid phase, was derived from the massic energy of combustion, in oxygen, at T = 298.15 K, measured by static bomb combustion calorimetry. The standard molar enthalpy of vaporization, at T = 298.15 K, was measured by Calvet microcalorimetry. From these two parameters the standard (p° = 0.1 MPa) molar enthalpy of formation, in the gaseous phase, at T = 298.15 K, was derived: ?(96.1 ± 3.4) kJ · mol^?1. The G3(MP2)//B3LYP composite method and appropriate reactions were used to computationally calculate the standard molar enthalpy of formation of 1-benzosuberone, in the gaseous phase, at T = 298.15 K. The computational results are in very good agreement with the experimental value.     

Vapour pressures of n-hexane determined by comparative ebulliometry

The vapour pressures of n-hexane have been measured using comparative ebulliometry with water as the reference fluid. The measurements cover the temperature and pressure range (315.7 K, 41.1 kPa) to (504.0 K, 2876.8 kPa) and join smoothly with results selected from the literature to provide consistent results down to (289.7 K, 13.8 kPa). The combined data set have been described by a Wagner style equation with a fractional standard deviation of 4.2 · 10⁻⁵ in the vapour pressure. The critical pressure p_c was treated as an adjustable parameter and the value of p_c = 3027 kPa was calculated from the smoothing equation using a selected critical temperature of T_c = 507.49 K. The calculated normal boiling temperature is T_b = 341.866 K and an extrapolation to the triple-point temperature T_tp = 177.87 K predicts a triple-point pressure of p_tp = 1.23 Pa.     

Thermodynamic study of the sublimation of crystalline tris(1,1,1-trifluoro-2,4-pentanedionate)ruthenium(III) and tris(1,1,1,5,5,5-hexafluoro-2,4-pentanedionate)ruthenium(III)

The Knudsen mass-loss effusion technique was used to measure the vapour pressures at different temperatures of two crystalline ruthenium complexes: tris(1,1,1-trifluoro-2,4-pentanedionate)ruthenium(III) {Ru(tfacac)₃}, between T =  350.20 K and T =  369.17 K and tris(1,1,1,5,5,5-hexafluoro-2,4-pentanedionate)ruthenium(III) {Ru(hfacac)₃} between T =  299.15 K and T =  313.14 K. From the temperature dependence of the vapour pressure of the crystalline compounds, the standard molar enthalpies of sublimation were derived by the Clausius–Clapeyron equation and the molar entropies of sublimation at equilibrium pressures were calculated. By using an estimated value for the heat capacity differences between the gas and the crystal phases the standard, p^o =  10⁵Pa, molar enthalpies, entropies, and Gibbs energies of sublimation at T =  298.15 K, were derived:     

Density and surface tension of pure 1-ethyl-3-methylimidazolium l-lactate ionic liquid and its binary mixtures with water

The density and surface tension of 1-ethyl-3-methylimidazolium l-lactate ([emim][l-lactate]) ionic liquid were determined from T = (283.15 to 333.15) K. The coefficients of thermal expansion were calculated from the experimental density results using an empirical correlation for T = (283.15 to 333.15) K. Molecular volume and standard entropies of the IL were calculated from the experimental density values. The surface properties of IL were investigated. The critical temperature and enthalpy of vaporization were also discussed. Density and surface tension have been measured over the whole composition range for {[emim][l-lactate] + water} binary systems at a temperature of 298.15 K and atmospheric pressure. Excess molar volumes V^E and the surface tension deviations δγ have been determined.     

Thermodynamic study on the sublimation of succinic acid and of methyl- and dimethyl-substituted succinic and glutaric acids

The Knudsen mass-loss effusion technique was used to measure the vapour pressures at different temperatures of the following crystalline dicarboxylic acids: succinic acid, between T =  360.11 K and T =  375.14 K; methylsuccinic acid, between T =  343.12 K and T =  360.11 K; 2,2-dimethylsuccinic acid, between T =  350.11 K, and T =  365.11 K; 2-methylglutaric acid, between T =  338.38 K and T =  347.63 K; and 2,2-dimethylglutaric acid between T =  342.18 K and T =  352.66 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, entropies and Gibbs energies of sublimation at T =  298.15 K, were derived:     

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.