Density,viscosity, and saturated vapor pressure of ethyl trifluoroacetate

The properties of ethyl trifluoroacetate (CF₃COOCH₂CH₃) were measured as a function of temperature: density (278.08 to 322.50) K, viscosity (293.45 to 334.32) K, saturated vapor pressure (293.35 to 335.65) K. The density data were fitted to a quadratic polynomial equation, and the viscosity data were regressed to the Andrade equation. The correlation coefficient (R²) of equations for density and viscosity are 0.9997 and 0.9999, respectively. The correlation between saturated vapor pressures and temperatures was achieved with a maximum absolute relative deviation of 0.142%. In addition, the molar evaporation enthalpy in the range of T = (293.35 to 335.65) K was estimated by the Clausius–Clapeyron equation.     

Thermodynamic properties of 4-tert-butyl-diphenyl oxide

The main thermodynamic functions (changes of the entropy, enthalpy, and Gibbs free energy) and functions of formation at T = 298.15 K of 4-tert-butyl-diphenyl oxide in condensed and ideal gas states were computed on the basis of experimental results obtained. The heat capacities of 4-tert-butyl-diphenyl oxide was measured by vacuum adiabatic calorimetry over the temperature range (8 to 371) K. The temperature, the enthalpy and the entropy of fusion were determined. The energy of combustion of the sample was determined by static-bomb combustion calorimetry. The saturation vapor pressures of the substance were measured by dynamic transpiration method over the temperature and pressure intervals (298 to 325) K and (0.05 to 1.2) Pa. The enthalpy of sublimation at T = 298.15 K was derived. The contribution of O-(2C_b) group (where C_b is the carbon atom in a benzene ring) into the absolute entropies of diphenyl oxide derivatives was assessed.     

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 selected organic compounds down to 1 mPa,using mass-loss Knudsen effusion method

A recently developed Knudsen effusion apparatus was improved and used for measurements of vapour pressures of selected organic compounds. Calorimetric studies were conducted using a Calvet-type calorimeter, complementing the information obtained for the vapour pressures and facilitating the modelling and analysis of the data.Vapour pressures of benzoic acid, a reference substance, were determined at temperatures between 269 K and 317 K, corresponding to a pressure range from 2 mPa to 1 Pa, extending the range of results available in the literature to lower pressures. Benzanthrone was studied between temperatures 360 K and 410 K (5 mPa–1 Pa) in order to test the apparatus at higher temperatures.Values presented in the literature for the vapour pressure of solid n-octadecane, one of the most promising compounds to be used as “phase change material” for textile applications, were found inconsistent with the triple point of the substance. Sublimation pressures were measured for this compound between T = 286 K and 298 K (2–20 mPa) allowing the correction of the existing values. Finally, vapour pressures of diphenyl carbonate, a compound of high industrial relevance for its use in the production of polycarbonates, were determined from T = 302 K to 332 K (0.02–1 Pa).     

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.     

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.     

New Knudsen effusion apparatus with simultaneous gravimetric and quartz crystal microbalance mass loss detection

A new Knudsen effusion apparatus, enabling simultaneous gravimetric and quartz crystal microbalance mass loss detection, is described. This device allows the measurement of vapour pressures of small sample mass (50 to 100) mg over a wide temperature range (350 to 650) K using very short effusion time intervals. The performance of the apparatus was checked by measuring the vapour pressures of anthracene, benzanthrone, and 1,3,5-triphenylbenzene, between (0.1 and 1) Pa, over temperature intervals of 20 K. The derived standard molar enthalpies of sublimation and vapour pressures are in excellent agreement with the mean of the available literature values and with the recommended values. The new working methodology and design of this apparatus allows the measurement of high quality vapour pressure data due to: accurate temperature measurement and control; improvement in vacuum thermal contact between the effusion cell and the oven metal block; optimisation of the quartz crystal sensor head microbalance position; efficient temperature control of the quartz crystal microbalance head; accurate measurement of the resonance crystal frequency using an impedance circuit analyser methodology.     

Enthalpy of solution of CO2 in aqueous solutions of methyldiethanolamine at T = 372.9 K and pressures up to 5 MPa

Experimental enthalpies of solution of CO₂ in aqueous solution of methyldiethanolamine (MDEA) of 15 wt% and 30 wt% are reported. The measurements were performed using a flow calorimetric technique at temperature of 372.9 K and pressures range from 0.5 MPa to 5 MPa. Gas solubilities data at same temperature and pressures were derived from the enthalpy data. Experimental enthalpies of solution are combined with available literature data in order to examine pressure and composition influences.     

Experimental and theoretical study of thermodynamic properties of levoglucosan

The heat capacity of levoglucosan was measured over the temperature range (5 to 370) K by adiabatic calorimetry. The temperatures and enthalpies of a solid-phase transition and fusion for the compound were found by DSC. The obtained results allowed us to calculate thermodynamic properties of crystalline levoglucosan in the temperature range (0 to 384) K. The enthalpy of sublimation for the low-temperature crystal phase was found from the temperature-dependent saturated vapor pressures determined by the Knudsen effusion method. The thermodynamic properties of gaseous levoglucosan were calculated by methods of statistical thermodynamics using the molecular parameters from quantum chemical calculations. The enthalpy of formation of the crystalline compound was found from the experiments in a combustion calorimeter. The gas-phase enthalpy of formation was also obtained at the G4 level of theory. The thermodynamic analysis of equilibria of levoglucosan formation from cellulose, starch, and glucose was conducted.     

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.     

Vapor pressures and sublimation enthalpies of seven heteroatomic aromatic hydrocarbons measured using the Knudsen effusion technique

The vapor pressures of seven heteroatom-containing cyclic aromatic hydrocarbons, ranging in molecular weight from (168.19 to 208.21) g · mol^?1 were measured over the temperature range of (301 to 486) K using the isothermal Knudsen effusion technique. The compounds measured include: anthraquinone, 9-fluorenone, 9-fluorenone oxime, phenoxazine, phenoxathiin, and 9H-pyrido[3,4-b]indole. These solid-state sublimation measurements provided values that are compared to vapor pressures of parent aromatic compounds (anthracene and fluorene) and to others with substituent groups in order to examine the effects of alcohol, ketone, pyridine, and pyrrole functionality on this property. The enthalpies and entropies of sublimation for each compound were determined from the Clausius–Clapeyron equation. Though there is no consistent trend in terms of the effects of substitutions on changes in the enthalpy or entropy of sublimation, we note that the prevalence of enthalpic or entropic driving forces on vapor pressure depend on molecule-specific factors and not merely molecular weight of the substituents.     

Simultaneous solubility of SO2 and NH3 in (salt + H2O) and enthalpy change upon dilution of (SO2 + NH3 + salt + H2O) in (salt + H2O) {salt = (NH4)2SO4 or Na2SO4}: Experimental results and model predictions

The simultaneous solubility of sulfur dioxide and ammonia in aqueous solutions of (ammonium sulfate or sodium sulfate) was measured by a synthetic method in the temperature range from 313.6 to 373.2 K and at pressures up to 2.5 MPa. Furthermore, the enthalpy change upon diluting aqueous solutions of sulfur dioxide, ammonia and (ammonium sulfate or sodium sulfate) in aqueous solutions of the same salt was measured in a batch calorimeter at about 313 and 352 K. The experimental results are used for comparison with predictions from a thermodynamic model for the vapor–liquid equilibrium and the enthalpy of dilution of those chemical reacting systems. In that model, activity coefficients are calculated from Pitzer's molality-scale-based Gibbs excess energy model, where all interaction parameters are either adopted from previous investigations on the properties of the binary and ternary sub-systems (if available) or they are neglected (if they are not available).     

Thermodynamic properties of the methyl esters of p-hydroxy and p-methoxy benzoic acids

The vapor pressures of crystalline and liquid phases of methyl p-hydroxybenzoate and of methyl p-methoxybenzoate were measured over the temperature ranges (338.9 to 423.7) K and (292.0 to 355.7) K respectively, using a static method based on diaphragm capacitance gauges. The vapor pressures of the crystalline phase of the former compound were also measured in the temperature range (323.1 to 345.2) K using a Knudsen mass-loss effusion technique. The results enabled the determination of the standard molar enthalpies, entropies and Gibbs free energies of sublimation and of vaporization, at T = 298.15 K, as well as phase diagram representations of the (p, T) experimental data, including the triple point. The temperatures and molar enthalpies of fusion of both compounds were determined using differential scanning calorimetry and were compared with the results indirectly derived from the vapor pressure measurements. The standard (p° = 10⁵ Pa) molar enthalpies 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 results, 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 quantum chemical computational calculations. A good agreement between experimental and theoretical results is observed. To analyze the thermodynamic stability of the two compounds studied, the standard Gibbs free energies of formation in crystalline and gaseous phases were undertaken. The standard molar enthalpies of formation of the title compounds were also estimated from two different computational approaches using density functional theory-based B3LYP and the multilevel G3 methodologies.     

The design,construction, and testing of a new Knudsen effusion apparatus

A new Knudsen effusion apparatus, enabling the simultaneous operation of nine effusion cells at three different temperatures, is fully described. The performance of the new apparatus was checked by measuring the vapour pressures, between 0.1 Pa and 1 Pa, over ca. 20 K temperature intervals of benzoic acid, phenanthrene, anthracene, benzanthrone, and 1,3,5-triphenylbenzene. The derived standard molar enthalpies of sublimation are in excellent agreement with the mean of the literature values available for these five compounds and with the recommended values for four of them.     

Complementary vapor pressure data for 2-methyl-1-propanol and 3-methyl-1-butanol at a pressure range of (15 to 177) kPa

The vapor pressure of pure 2-methyl-1-propanol and 3-methyl-1-butanol, components called congeners that are present in aroma of wine, pisco, and other alcoholic beverages, were measured with a dynamic recirculation apparatus at a pressure range of (15 to 177) kPa with an estimated uncertainty <0.2%. The measurements were performed at temperature ranges of (337 to 392) K for 2-methyl-1-propanol and (358 to 422) K for 3-methyl-1-butanol. Data were correlated using a Wagner-type equation with standard deviations of 0.09 kPa for the vapor pressure of 2-methyl-1-propanol and 0.21 kPa for 3-methyl-1-butanol. The experimental data and correlation were compared with data selected from the literature.     

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.     

Acoustic,volumetric and osmotic properties of binary mixtures containing the ionic liquid 1-butyl-3-methylimidazolium dicyanamide mixed with primary and secondary alcohols

In this paper, densities and speeds of sound for five binary systems {alcohol + 1-butyl-3-methylimidazolium dicyanamide} were measured from T = (293.15 to 323.15) K and atmospheric pressure. From these experimental data, apparent molar volume and apparent molar isentropic compression have been calculated and fitted to a Redlich–Meyer type equation. This fit was also used to calculate the apparent molar volume and apparent molar isentropic compression at infinite dilution for the studied binary mixtures. Moreover, the osmotic and activity coefficients and vapor pressures of these binary mixtures were also determined at T = 323.15 K using the vapor pressure osmometry technique. The experimental osmotic coefficients were correlated using the Extended Pitzer model of Archer. The mean molal activity coefficients and the excess Gibbs free energy for the studied mixtures were calculated from the parameters obtained in the correlation.     

Vapor–liquid equilibria in the binary system (−)-beta-pinene + (+)-fenchone: Analysis in terms of group contributions models of some binary systems containing terpenoids

Isobaric vapor–liquid equilibrium measurements are reported for the binary system (−)-beta-pinene + (+)-fenchone at the constant pressure of 13.33 kPa in the temperature range from 341.60 K to 393.25 K. The boiling temperatures of the mixtures were also measured at seven constant compositions in the pressure range from 2.56 kPa to 20.80 kPa. The experimental data were found to be thermodynamically consistent. Reduction of the vapor–liquid equilibrium data was carried out by means of the Wilson, NRTL and UNIQUAC equations. Our data on vapor–liquid equilibria for mixtures containing terpenoids are examined in terms of the DISQUAC and modified UNIFAC (Dortmund) group contributions models. Interaction parameters of the DISQUAC model are reported.