The Journal of Chemical Thermodynamics

Published by Elsevier
Online ISSN: 1096-3626
Print ISSN: 0021-9614
The pH values of two buffer solutions without NaCl and seven buffer solutions with added NaCl, having ionic strengths (I = 0.16 mol·kg(-1)) similar to those of physiological fluids, have been evaluated at 12 temperatures from T = (278.15 to 328.15) K by way of the extended form of the Debye-Hückel equation of the Bates-Guggenheim convention. The residual liquid junction potentials (δE(j)) between the buffer solutions of TRICINE and saturated KCl solution of the calomel electrode at T = (298.15 and 310.15) K have been estimated by measurement with a flowing junction cell. For the buffer solutions with the molality of TRICINE (m(1)) = 0.06 mol·kg(-1), NaTRICINE (m(2)) = 0.02 mol·kg(-1), and NaCl (m(3)) = 0.14 mol·kg(-1), the pH values at 310.15 K obtained from the extended Debye-Hückel equation and the inclusion of the liquid junction correction are 7.342 and 7.342, respectively. These are in excellent agreement. The zwitterionic buffer TRICINE is recommended as a secondary pH standard in the region for clinical application.
This paper reports the pH values of five NaCl-free buffer solutions and eleven buffer compositions containing NaCl at I = 0.16 mol·kg(-1). Conventional pa(H) values are reported for sixteen buffer solutions with and without NaCl salt. The operational pH values have been calculated for five buffer solutions and are recommended as pH standards at T = (298.15 and 310.15) K after correcting the liquid junction potentials. For buffer solutions with the composition m(1) = 0.04 mol·kg(-1), m(2) = 0.08 mol·kg(-1), m(3) = 0.08 mol·kg(-1) at I = 0.16 mol·kg(-1), the pH at 310.15 K is 7.269, which is close to 7.407, the pH of blood serum. It is recommended as a pH standard for biological specimens.
Densities of dilute aqueous solutions of isopropanol, 1,5-pentanediol, cyclohexanol, benzyl alcohol, diethyl ether, 1,2-dimethoxyethane, acetone, and 2,5-hexanedione were measured by means of a vibrating-tube flow densimeter at temperatures near T = (302, 373, 423, 473, and 521) K at a pressure of p = 28 MPa. At the lowest and highest temperatures, measurements were also made close to the saturation vapour pressure of water to investigate the effect of pressure on the volumes of solutes. Apparent molar volumes were calculated for each solute and extrapolated to give partial molar volumes at infinite dilution. The variation of the volume with temperature, pressure, and structure of solute is discussed qualitatively, and group contributions are determined at the temperatures of measurements and p = 28 MPa. Several equations proposed in the literature for correlating the partial molar volumes at infinite dilution as a function of state parameters are tested. Parameters of one selected equation are tabulated allowing calculation of the partial molar volumes at infinite dilution at temperatures and pressures up to T = 573 K and p = 40 MPa. respectively.
To characterize better the thermodynamic behavior of a binary polycyclic aromatic hydrocarbon mixture, thermochemical and vapor pressure experiments were used to examine the phase behavior of the {anthracene (1) + benzo[a]pyrene (2)} system. A solid-liquid phase diagram was mapped for the mixture. A eutectic point occurs at x(1) = 0.26. The eutectic mixture is an amorphous solid that lacks organized crystal structure and melts between T = (414 and 420) K. For mixtures that contain 0.10 < x(1) < 0.90, the enthalpy of fusion is dominated by that of the eutectic. Solid-vapor equilibrium studies show that mixtures of anthracene and benzo[a]pyrene at x(1) < 0.10 sublime at the vapor pressure of pure benzo[a]pyrene. These results suggest that the solid-vapor equilibrium of benzo[a]pyrene is not significantly influenced by moderate levels of anthracene in the crystal structure.
Despite the relatively small atomic fraction of a given heteroatom in a binary mixture of polycyclic aromatic compounds (PAC), the inclusion of heteroatomic substituted compounds can significantly impact mixture vapor pressure behavior over a wide range of temperatures. The vapor pressures of several binary PAC mixtures containing various heteroatoms show varying behavior, from practically ideal behavior following Raoult's law to significant deviations from ideality depending on the heteroatom(s) present in the mixture. Mixtures were synthesized using the quench-cool technique with equimolar amounts of two PAC, both containing heteroatoms such as aldehyde, carboxyl, nitrogen, and sulfur substituent groups. For some mixtures, deviation from ideality is inversely related to temperature, though in other cases we see deviations from ideality increasing with temperature, whereas some appear independent of temperature. Most commonly we see lower vapor pressures than predicted by Raoult's law, which indicates that the interacting heteroatoms prefer the solid mixture phase as opposed to the vapor phase. Although negative deviations predominate from Raoult's Law, the varying mixtures investigated show both higher and lower enthalpies and entropies of sublimation than predicted. In each mixture, a higher enthalpy of sublimation leads to higher entropy of sublimation than predicted, and vice versa.
Knowledge of vapor pressures of high molar mass organics is essential to predicting their behavior in combustion systems as well as their fate and transport within the environment. This study involved polycyclic aromatic compounds (PACs) containing halogen hetero-atoms, including bromine and chlorine. The vapor pressures of eight PACs, ranging in molar mass from (212-336) g.mol(-1), were measured using the isothermal Knudsen Effusion technique over the temperature range of (296-408) K. These compounds included those with few or no data available in the literature, namely: 1,4-dibromonaphthalene; 5-bromoacenaphthene; 9-bromoanthracene; 1,5-dibromoanthracene; 9,10-dibromoanthracene; 2-chloroanthracene; 9,10-dichloroanthracene and 1-bromopyrene. Enthalpies of sublimation of these compounds were determined via application of the Clausius-Clapeyron equation. An analysis is presented on the effects of the addition of halogen hetero-atoms to pure polycyclic aromatic hydrocarbons using these data as well as available literature data. As expected, the addition of halogens onto these PACs increases their enthalpies of sublimation and decreases their vapor pressures as compared to the parent compounds.
The vapor pressures of seven heteroatom-containing cyclic aromatic hydrocarbons, ranging in molecular weight from (168.19 to 208.21) grams plus sign in circlemol(-1) were measured over the temperature range of (301 to 486) Kelvin 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.
Isothermal titration calorimetry (ITC) is a traditional and powerful method for studying the linkage of ligand binding to proton uptake or release. The theoretical framework has been developed for more than two decades and numerous applications have appeared. In the current work, we explored strategic aspects of experimental design. To this end, we simulated families of ITC data sets that embed different strategies with regard to the number of experiments, range of experimental pH, buffer ionization enthalpy, and temperature. We then re-analyzed the families of data sets in the context of global analysis, employing a proton linkage binding model implemented in the global data analysis platform SEDPHAT, and examined the information content of all data sets by a detailed statistical error analysis of the parameter estimates. In particular, we studied the impact of different assumptions about the knowledge of the exact concentrations of the components, which in practice presents an experimental limitation for many systems. For example, the uncertainty in concentration may reflect imperfectly known extinction coefficients and stock concentrations or may account for different extents of partial inactivation when working with proteins at different pH values. Our results show that the global analysis can yield reliable estimates of the thermodynamic parameters for intrinsic binding and protonation, and that in the context of the global analysis the exact molecular component concentrations may not be required. Additionally, a comparison of data from different experimental strategies illustrates the benefit of conducting experiments at a range of temperatures.
Integral molar enthalpies of mixing were determined by drop calorimetry for Cu-Li-Sn at 1073 K along five sections x Cu/x Sn ≈ 1:1, x Cu/x Sn ≈ 2:3, x Cu/x Sn ≈ 1:4, x Li/x Sn ≈ 1:1, and x Li/x Sn ≈ 1:4. The integral and partial molar mixing enthalpies of Cu-Li and Li-Sn were measured at the same temperature, for Li-Sn in addition at 773 K. All binary data could be described by Redlich-Kister-polynomials. Cu-Li shows an endothermic mixing effect with a maximum in the integral molar mixing enthalpy of ∼5300 J · mol(-1) at x Cu = 0.5, Li-Sn an exothermic minimum of ∼ -37,000 J · mol(-1) at x Sn ∼ 0.2. For Li-Sn no significant temperature dependence between 773 K and 1073 K could be deduced. Our measured ternary data were fitted on the basis of an extended Redlich-Kister-Muggianu model for substitutional solutions. Additionally, a comparison of these results to the extrapolation model of Chou is given.
The present work refers to high-temperature drop calorimetric measurements on liquid Al-Cu, Al-Sn, and Al-Cu-Sn alloys. The binary systems have been investigated at 973 K, up to 40 at.% Cu in case of Al-Cu, and over the entire concentrational range in case of Al-Sn. Measurements in the ternary Al-Cu-Sn system were performed along the following cross-sections: x(Al)/x(Cu) = 1:1, x(Al)/x(Sn) = 1:1, x(Cu)/x(Sn) = 7:3, x(Cu)/x(Sn) = 1:1, and x(Cu)/x(Sn) = 3:7 at 1273 K. Experimental data were used to find ternary interaction parameters by applying the Redlich-Kister-Muggianu model for substitutional solutions, and a full set of parameters describing the concentration dependence of the enthalpy of mixing was derived. From these, the isoenthalpy curves were constructed for 1273 K. The ternary system shows an exothermic enthalpy minimum of approx. -18,000 J/mol in the Al-Cu binary and a maximum of approx. 4000 J/mol in the Al-Sn binary system. The Al-Cu-Sn system is characterized by considerable repulsive ternary interactions as shown by the positive ternary interaction parameters.
Polycyclic aromatic hydrocarbons (PAHs) are compounds resulting from incomplete combustion and many fuel processing operations, and they are commonly found as subsurface environmental contaminants at sites of former manufactured gas plants. Knowledge of their vapor pressures is the key to predict their fate and transport in the environment. The present study involves five heavy PAHs, i.e. benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[ghi]perylene, indeno[1,2,3-cd]pyrene, and dibenz[a,h]anthracene, which are all as priority pollutants classified by the US EPA. The vapor pressures of these heavy PAHs were measured by using Knudsen effusion method over the temperature range of 364 K to 454 K. The corresponding values of the enthalpy of sublimation were calculated from the Clausius-Clapeyron equation. The enthalpy of fusion for the 5 PAHs was also measured by using differential scanning calorimetry and used to convert earlier published sub-cooled liquid vapor pressure data to solid vapor pressure in order to compare with the present results. These adjusted values do not agree with the present measured actual solid vapor pressure values for these PAHs, but there is good agreement between present results and other earlier published sublimation data.
A vibrating-tube densimeter was used to measure differences between the density of NaCl(aq) and water from 0.0025 to 5.0 mol · kg−1, 323 to 600 K, and 0.1 to 40 MPa. The results were represented by a multi-dimensional cubic-spline surface fitted to the apparent molar volumes with inclusion of the Debye-Hückel limiting-law slopes. Attention has been paid to a proper weighting of results with consideration of uncertainties in all measured variables. Recommended values of apparent molar volume were generated from the knots characterizing the surface. The results compare well with most recommended values published earlier and yield new information on volumetric properties of NaCl solutions at high temperatures.
Measurements of ultrasonic speed were carried out for (n-pentane + n-hexane + benzene), (n-hexane + cyclohexane + benzene), and (cyclohexane + n-heptane + toluene) at (298.15±0.01) K. The ultrasonic speeds of these mixtures were also evaluated theoretically from various empirical, semi-empirical, and statistical models. The agreement between theoretical and experimental values is fair for all the mixtures. An attempt has also been made to explain the nature of intermolecular interactions in the light of excess isentropic compressibilities.
The difference in heat capacity between water and 0.0150 mol·kg−1 NaCl(aq) was measured from 604 to 718 K at 32 MPa with a modified flow calorimeter. The apparent molar heat capacities of NaCl(aq) calculated from these results drop quickly to a minimum. Cp, φ = −18000 J·K−1·mol−1 at 668 K, rise to a maximum Cp, φ = 12000 J·K−1·mol−1 at 686 K, and then decrease. These very large and rapidly varying effects are due to the proximity to the critical point of the solvent. The qualitative behavior of Cp, φ is predicted by theories of dilute solutions near the critical point of the solvent. The magnitude of the effects are not predicted by these theories. These are the first measurements of heat capacities of aqueous solutions near the critical point of water.
Viscosity of nine aqueous Ni(NO3)2 solutions (0.050, 0.153, 0.218, 0.288, 0.608, 0.951, 1.368, 1.824, and 2.246) mol · kg−1 was measured in the temperature range from (297 to 475) K and at pressures (0.1, 10, 20, and 30) MPa. The measurements were carried out with a capillary flow technique. The total experimental uncertainty of viscosity, pressure, temperature, and composition measurements were estimated to be less than 1.6%, 0.05%, 15 mK, and 0.02%, respectively. All experimental and derived results are compared with experimental and calculated values reported in the literature. Extrapolation of the solution viscosity measurements to zero concentration (pure water values) for the given temperature and pressure are in excellent agreement (average absolute deviation, AAD = 0.13%) with the values of pure water viscosity from IAPWS formulation [J. Kestin, J.V. Sengers, B. Kamgar-Parsi, J.M.H. Levelt Sengers, J. Phys. Chem. Ref. Data 13 (1984) 175–189]. The viscosity data for the solutions as a function of concentration have been interpreted in terms of the extended Jones–Dole equation for strong electrolytes. The values of viscosity A-, B-, and D-coefficients of the extended Jones–Dole equation for the relative viscosity (η/η0) of aqueous Ni(NO3)2 solutions as a function of temperature are studied. The derived values of the viscosity A- and B-coefficients were compared with the results predicted by Falkenhagen–Dole theory (limiting law) of electrolyte solutions and the values calculated with the ionic B-coefficient data. The measured values of viscosity for the solutions were also used to calculate the effective rigid molar volumes in the extended Einstein relation for the relative viscosity (η/η0).
Ternary (liquid + liquid) equilibrium data are presented for mixtures of 1-hexyl-3-methylimidazolium (tetrafluoroborate or hexafluorophosphate) + benzene + (heptane or dodecane or hexadecane) at T=298.2 K. The tie line compositions of the conjugate solutions were obtained by means of density measurements and a standard density calibration curve. Large regions of immiscibility (increasing in the order of hexadecane > dodecane > heptane) and favourable skewing of the tie lines towards the solvent axis provide indications of the favourable use of the ionic liquids in solvent extraction. Selectivity values computed from the experimental data confirm this. Correlation of the experimental tie lines was conducted through the use of the NTRL equation, which provides good correlation of the experimental data.
Relative densities and relative massic heat capacities have been measured for acidified solutions of Y(NO3)3(aq), Pr(NO3)3(aq), and Gd(NO3)3(aq) at T = (288.15, 298.15, 313.15, and 328.15) K and p = 0.1 MPa. In addition, relative densities and massic heat capacities have been measured at the same temperatures and pressure for Y(NO3)3(aq) and Ho(NO3)3(aq) solutions without excess acid (n.b. measurements at T = 328.15 K for Ho(NO3)3(aq) were not performed due to the limited volume of solution available). Apparent molar volumes and apparent molar heat capacities for the aqueous salt solutions have been calculated from the experimental apparent molar properties of the acidified solutions using Young’s rule, whereas the apparent molar properties of the solutions without excess acid were calculated directly from the measured densities and massic heat capacities. The two sets of data for the Y(NO3)3(aq) systems provide a check of the internal consistency of the Young’s rule approach we have utilised.The concentration dependences of the apparent molar volumes and heat capacities of the aqueous salt solutions have been modelled at each investigated temperature using the Pitzer ion interaction equations to yield apparent molar properties at infinite dilution.Complex formation within the aqueous rare earth nitrate systems is discussed qualitatively by probing the concentration dependence of apparent molar volumes and heat capacities. In spite of the complex formation in the aqueous rare earth nitrate systems, there is a high degree of self-consistency between the apparent molar volumes and heat capacities at infinite dilution reported in this manuscript and those previously reported for aqueous rare earth perchlorates.
Thermophysical properties are central to process engineering design. In process flowsheeting these properties are represented by thermodynamic models, which are derived from a combination of theory and experimental phase equilibria. Phase equilibrium measurements on (methanethiol or ethanethiol or propan-1-thiol or butan-1-thiol + n-hexane or n-decane or toluene or water) have been made on a static system, at mole fractions 0 to 0.2 of thiol over a temperature range of 323 to 373 K.
New measurements of the molar volume of (0.476Ar + 0.524N2)(1) at the temperature 119.33 K and at pressures from close to the vapour pressure up to 145 MPa are reported in this work. They were used, together with results from other authors, to fit parameters for the cross intermolecular potential, in the framework of the van der Waals one-fluid model. Using the same procedure for the binaries (oxygen + nitrogen) and (argon + oxygen) molar volumes and molar residual enthalpies of liquid air were then calculated for pressures up to 80 MPa and compared with correlation results.
Measurements of (p, ϱ, T) have been made on c-C6H12 and on (0.501c-C6H12 + 0.499n-C7H16) as a function of temperature (from 295 to 355 K) and pressures up to 100 MPa by means of a magnetic-suspension method. Excess molar volumes have also been derived and their qualitative behaviour is discussed.
Henry’s law constants and infinite dilution activity coefficients of cis-2-butene, dimethylether, chloroethane, and 1,1-difluoroethane in methanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, tert-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol, and 2-methyl-2-butanol in the temperature range of 250 K to 330 K were measured by a gas stripping method and partial molar excess enthalpies were calculated from the activity coefficients. A rigorous formula for evaluating the Henry’s law constants from the gas stripping measurements was used for the data reduction of these highly volatile mixtures. The uncertainty is about 2% for the Henry’s law constants and 3% for the estimated infinite dilution activity coefficients. In the evaluation of the infinite dilution activity coefficients, the nonideality of the solute such as the fugacity coefficient and Poynting correction factor cannot be neglected, especially at higher temperatures. The estimated uncertainty of the infinite dilution activity coefficients includes 1% for nonideality.
The vapour pressures of the environmentally safe refrigerants 1,1,1,2-tetrafluoroethane (R 134a) and 1,1-difluoroethane (R 152a) were measured. For R 134a, 37 values were obtained for temperatures between 303 K and the critical temperature Tc = 374.18 K. For R 152a, 55 vapour pressures were measured between 301 K and the critical temperature Tc = 386.41 K. The uncertainities of temperature and pressure measurements are estimated to be 5 nK and 0.0001·p, respectively, resulting in a final uncertainty of 0.0002·pσ or less for the vapour pressure pσ. Wagner-type vapour-pressure equations were fitted to the new results and to values from other research groups.
Extensive measurements of (p, ρ, T) in the gas phase of the refrigerants R 134a and R 152a were performed with a Burnett apparatus. For R 134a, a total of 411 points located on 19 isotherms between 293.15 K and 453.15 K were obtained at pressures between 0.1 MPa and 16 MPa. A total of 335 (p, ρ, T) triplets for R 152a were determined in the same pressure range on 17 isotherms between 293.15 K and 433.15 K. Estimated uncertainties of temperature, pressure, and density are 5 mK, 0.0001 · p, and 0.0003 · ρ, respectively. The new (p, ρ, T) results are represented by truncated virial equations of state within their estimated uncertainties for pressures up to 4.5 MPa. Second virial coefficients obtained during reduction of Burnett results show good agreement with second virial coefficients reported by other research groups mostly derived from speed-of-sound measurements.
Excess molar enthalpies for the binary systems: (ethyl 1,1-dimethylethyl ether + heptane); (ethyl 1,1-dimethylethyl ether + cyclohexane); (ethyl 1,1-dimethylethyl ether + toluene); (cyclohexane + toluene), and (toluene + heptane) have been measured at T = (298.15 and 313.15) K using a new isothermal flow calorimeter developed in the laboratory. The technique was previously checked by measuring test systems. The experimental results have been correlated with the Redlich–Kister polynomial equation. The mixing effects observed and the influence of the temperature are discussed.
The speed of sound in gaseous 1,1,1-trifluoroethane has been obtained at temperatures between (270 and 370) K from measurements of the resonance frequency of the radial modes of a spherical resonator. Ideal gas heat capacities and acoustic virial coefficients have been calculated from the results. The acoustic data have been used to determine density virial coefficients with a hard-core square-well intermolecular potential equation of state.A Helmholtz energy equation of state is proposed, whose parameters are directly fitted to the present speed of sound data and uses the acoustically determined temperature dependence of the perfect gas heat capacity. The Helmholtz equation so obtained compares favourably with other conventional methods and provides a high accuracy equation specific for the vapour phase of the fluid. The performance of the equation, in terms of the accuracy of the thermodynamic properties derived from it, has been determined by comparison of predicted densities with available experimental data. The equation of state shows very good extrapolation behaviour beyond the range of temperatures and pressures of the experimental data to which it was fitted.
The heat capacity of 1,1,1-trifluoro-3-chloropropane and 1,1,1,3-tetrachloropropane from 12 to 300 K and also the temperature and enthalpy of fusion of these compounds were measured in a vacuum adiabatic calorimeter. The results obtained were used for calculating the thermodynamic functions from 12 to 300 K and, in conjunction with literature data, for calculating ΔGfo(l, 298.15 K). 1,1,1-Trifluoro-3-chloropropane was found to undergo two solid-phase transitions, one transition being monotropic (T = (116.0 ± 0.1) K; ΔH′t = −(605 ± 9) calth mol−1), and the other, enantiotropic (T = (169.8 ± 0.1) K; ΔH″t = (1073 ± 4) calth mol−1). Only one solid-phase transition was found for 1,1,1,3-tetrachloropropane (T = (219.9 ± 0.1) K; ΔH″t = (527 ± 4) calth mol−1). Raman, i.r., and n.q.r. spectra of various phases point to the association of the observed solid-phase transitions with the transformations of conformers.
(Vapour+liquid) equilibrium (VLE) data were measured for the refrigerant mixture {dimethyl ether (RE170)+1,1,1,3,3,3-hexafluoropropane (R236fa)} at the temperatures (303.68 and 323.75) K. The VLE data were obtained using forced recirculation of the vapour through the liquid by means of a magnetic pump. The composition of both phases was determined by gas chromatography. The experimental VLE data are regressed using the Carnahan–Starling–De Santis equation of state, which was chosen for its ability to represent the volumetric properties along bubble and dew point curves. The experimental data show negative deviations from Raoult's law that can be attributed to hydrogen bonding between oxygen in RE170 (proton acceptor) and hydrogen (evidently a proton donor, judging from our measurements) in R236fa. VLE data of the studied system are not available elsewhere in the literature.
Excess molar volumes of (oxane + trichloromethane or tetrachloromethane or 1,2-dichloroethane or 1,1,2-trichloroethane or 1,1,2,2-tetrachloroethane or pentachloroethane) at 303.15 K are reported. The excess volume of (oxane + dichloroethane) is positive but all others are negative over the whole composition range. The excess volumes decrease as the number of chlorine atoms in the chloroalkane increases.
Excess volumes of 1,1,2,2-tetrachloroethane + cyclohexane, + benzene, + carbon tetrachloride; of tetrachloroethylene + cyclohexane, + benzene, + carbon tetrachloride; and 1,1,2,2-tetrachloroethane + tetrachloroethylene, have been measured at 303.15 K by a dilatometric method. For benzene + 1,1,2,2-tetrachloroethane some measurements have also been carried out at 313.15 K. The results obtained are related with the HE measurements for the same mixtures.
Measurements leading to the calculation of standard entropies for 1,10-phenanthroline (Chemical Abstracts registry number [66-71-7]) in the crystal, liquid, and ideal-gas state are reported. Experimental methods were adiabatic heat-capacity calorimetry and comparative ebulliometry. Thermodynamic properties for phenanthridine [229-87-8] and 7,8-benzoquinoline [230-27-3] were reported previously and included those measured with adiabatic heat-capacity calorimetry, comparative ebulliometry (7,8-benzoquinoline only), inclined-piston manometry, and combustion calorimetry. New measurement results for phenanthridine and 7,8-benzoquinoline reported here are densities determined with a vibrating-tube densimeter and heat capacities for the liquid phase at saturation pressure determined with a differential scanning calorimeter (dsc), and vapor pressures by comparative ebulliometry (phenanthridine only). All critical properties were estimated. Molar entropies for the ideal-gas state were derived for all compounds at selected temperatures. Independent calculations of entropies for the ideal-gas state were performed at the B3LYP/6-31+G(d,p) model chemistry for the three compounds studied. These are shown to be in excellent accord with the calorimetric results for 1,10-phenanthroline and phenanthridine. Results for 7,8-benzoquinoline indicate that the crystal state is disordered. All new experimental results are compared with property values reported in the literature.
The standard (po = 101.325 kPa) molar enthalpies of combustion in oxygen at 298.15 K were measured by static-bomb calorimetry and the standard molar enthalpies of sublimation at 298.15 K were measured by microcalorimetry for 1,2-dihydroxybenzene (catechol) and six alkylsubstituted catechols: View Within ArticleThe increment in the molar enthalpy of formation of the gaseous compound for substitution of alkyl-groups into catechol was found to be approximately the same as the corresponding increment for substitution into benzene.
Measurements leading to the calculation of the ideal-gas thermodynamic properties for 1,2,3,4- and 5,6,7,8-tetrahydroquinoline are reported. Thermochemical and thermophysical properties were determined by adiabatic heat-capacity calorimetry, comparative ebulliometry, inclined-piston-gauge manometry, and combustion calorimetry. Results were used to calculate standard entropies, enthalpies, and Gibbs energies of formation for the ideal-gas state at selected temperatures to 500 K. The results of the thermodynamic-property measurements were used to determine equilibrium constants, and hence, equilibrium molalities, for the quinoline/hydrogen/tetrahydroquinoline reaction network at temperatures of interest in the processing of fossil-fuel feedstocks with a high nitrogen content. The results show that under typical processing conditions (650 K and 7.0 MPa hydrogen pressure) there is thermodynamic equilibrium between quinoline and 1,2,3,4-tetrahydroquinoline. That equilibrium conditions exist between quinoline and 5,6,7,8-tetrahydroquinoline in processing is more equivocal; however, there is strong evidence for such an equilibrium.
The standard (p⊖ = 0.1 MPa) molar enthalpies of formation of 1,2,4-triazol-5-one and 3-nitro-1,2,4-trazol-5-one have been determined from measurements of their energies of combustion in oxygen as −(142.4±0.7) kJ · mol−1 and −(129.4±1.1) kJ · mol−1, respectively. From measurements of the enthalpies of neutralization of 3-nitro-1,2,4-triazol-5-one with NaOH(aq) and KOH(aq) the enthalpies of formation of the crystalline sodium and potassium salts have been determined as −(362.6±1.2) kJ · mol−1 and −(385.1±1.1) kJ · mol−1, respectively.
Densities of dilute solutions of 1,3-dimethyl-2-imiazolidinone in H2O and D2O, with the solute mole-fractions ranging up to 0.01, have been measured with an error of 1.5 · 10−5 g · cm−3 at (278.15, 288.15, 298.15, 308.15, 313.15, and 318.15) K and atmospheric pressure using a vibrating-tube densimeter. The partial molar volumes of the dissolved DMI (down to the infinite dilution) and solvent (H2O or D2O) as well as the excess molar volumes of the isotopically distinguishable solutions have been calculated. The effects of the solvent isotope substitution, solute concentration and temperature on the volume changes caused by DMI hydration have been considered. The obvious relationship between the D2O–H2O solvent isotope effects on the partial molar volume and enthalpy of solution of DMI has been discovered.
We used a vibrating tube densimeter (DMA 512P, Anton Paar, Austria) to investigate the densities and volumetric properties of aqueous 2-amino-2-hydroxymethyl-propan-1,3-diol (Tris or THAM) and THAM plus equimolal HCl. We made measurements at molalities m from (0.005 to 0.5)mol · kg − 1and at temperatures from 278.15 K to 393.15 K. We calibrated the densimeter through measurements on pure water and on 1.0 mol · kg − 1NaCl at the pressure 0.35 MPa. We used a fixed-cell, power-compensation, differential-output, temperature-scanning calorimeter (NanoDSC 6100, Calorimetry Sciences Corporation, Provo, UT, U.S.A.) to measure solution heat capacities at molalities from (0.005 to 0.5)mol · kg − 1and at temperatures from 278.15 K to 368.15 K. This was accomplished by scanning temperature and comparing the heat capacities of the unknown solutions to the heat capacity of water. We calculated the apparent molar volumes Vφand apparent molar heat capacitiesCp, φ of the solutions and fitted them to equations that describe the surfaces (Vφagainst T against m) and (Cp,φagainst T against m). Standard state partial molar volumesV2o and heat capacities Cp,2owere estimated by extrapolation to the m = 0 plane of the fitted surfaces. We used previously determinedCp, φ for HCl(aq) to obtainΔrCp, m for the proton dissociation reaction of THAM ·H + (aq). The (ΔrCp,magainst T against m) surface was created by subtracting Cp,φof THAM(aq) and HCl(aq) from the heat capacity of THAM ·HCl(aq). We created surfaces representing ΔrHmandpQa by integration of our ΔrCp,msurface over T while using values forΔrHm and pQaatT = 298.15 K from the literature as integration constants.
Densities, ρ, ultrasonic speeds, u, and viscosities, η, of aqueous-1,4-butanediol (20% and 40% w/w of 1,4-butanediol) and of solutions of glycine (Gly), dl-alanine (Ala), and l-valine (Val) in aqueous-1,4-butanediol were measured at T = (298.15, 303.15, 308.15, 313.15, and 318.15) K. From these experimental results, apparent molar volume, Vϕ, limiting apparent molar volume, and the slope, Sv, apparent molar compressibility, κϕ, limiting apparent molar compressibility, , and the slope, Sk, transfer volume, , Falkenhagen coefficient, A, Jones–Dole coefficient, B, free energies of activation of viscous flow per mole of solvent, and per mole of solute, were calculated. The results are interpreted from the point of view of solute–solvent and solute–solute interactions in these systems. It has been observed that there exist strong solute–solvent interactions in these systems, which increase with rise in temperature. For the amino acids studied, the values of follow the order: Gly < Ala < Val, indicating that the increased hydrophobic/non-polar character of the side chain of these amino acids causes a reduction in electrostriction at the terminal charged groups. These amino acids act as structure-breakers in aqueous-1,4-butanediol solvents. The thermodynamics of viscous flow has also been discussed.
The potential difference E of the amalgam cell {CsxHg1 − x|CsX (m)|AgX|Ag} (X = Cl, Br, I) has been measured as a function of the mole fraction xCs of Cs metal in amalgams and of the molality m of CsX in (methanol + water), (acetonitrile + water), and (1,4-dioxane + water) solvent mixtures containing up to 0.75 mass fraction of the organic component, at the temperature 298.15 K. The respective standard molal potential differences have been determined together with the relevant activity coefficients γ± as functions of the CsX molality. The found values show a parabolic decrease with increasing proportion of the organic component in the solvent mixture. Analysis of the relevant primary medium effects upon CsX shows that the CsX transfer from the standard state in water to the standard state in the (aqueous + organic) mixture is always unfavoured, and the acetonitrile is the least unfavoured co-solvent studied. Analysis of the primary medium effect upon CsI in terms of Feakins and French’s theory leads to a primary hydration number close to zero, which is consistent with the results of supplementary EXAFS experiments on Cs+ and I− in (acetonitrile + water) solvent mixtures.
The electromotive forces E of the amalgam cells {LixHg1 − x| LiCl(m)| AgCl | Ag} and {LixHg1 − x| LiBr(m)| AgBr | Ag} have been measured as a function of the mole fraction x of Li metal in amalgams and of the molalities m of LiCl as well as LiBr at T = 298.15 K. For LiCl, the solvents investigated have been (acetonitrile + water), (1,4-dioxane + water), and (methanol + water) mixtures containing up to mass fraction 0.8 of the organic component, but only (acetonitrile + water) mixtures for LiBr. The standard molal electromotive forces Emohave been determined and, for all the solvent systems explored, they appear to vary linearly with the mole fraction y of the organic component involved, according to the following equations: Emo(LiCl) / V = 2.4169 − 0.2961yA;Emo(LiCl) / V = 2.4175 − 0.5951yD;Emo(LiCl) / V = 2.4163 − 0.1749yM;Emo(LiBr) / V = 2.2672 − 0.2092yA, where A denotes acetonitrile, D is 1,4-dioxane, and M is methanol. The relevant mean molal activity coefficients as functions of the LiCl and LiBr molalities have also been determined. The primary medium effects upon LiCl and LiBr, analysed in terms of the Feakins–French theory, lead to primary hydration numbers of ≈ 5 for LiCl and ≈ 4 for LiBr. These are somewhat lower than those obtained by other methods, but their difference is expected considering the known primary hydration numbers of the anions Cl − and Br − .
The electromotive force E of the amalgam cell {KxHg1 − x| KCl(m)|AgCl|Ag} has been measured as a function of the mole fraction x of K metal in amalgams and of the molality m of KCl in (ethylene glycol + water), (acetonitrile + water), and (1,4- dioxane + water) solvent mixtures containing up to 0.8 mass fraction of the organic component, at the temperature 298.15 K. The respective standard electromotive forces Emohave been determined, together with the relevant activity coefficients γ ± as a function of KCl molality. A new scheme is here implemented for verification of the internal consistency of the γ ± results in terms of complementary pairs of concentration cells with transference. For interpolation purposes, the Emodependence on the mass fraction w of the organic component of the solvent mixture within the range explored may be expressed by:(the subscripts denoting G = ethylene glycol, A = acetonitrile, and D = 1,4-dioxane, respectively) which reproduce the observed Emovalues to within ± 0.3 mV. Analysis of the relevant primary medium effects upon KCl leads to a primary hydration number of 6.6 for KCl, in good agreement with previous results based on different methods.
The enthalpies of solution of 1,4-dioxane in {(1 − x)F + xH2O}, {(1 − x)NMF + xH2O}, and {(1 − x)DMF + xH2O} have been measured within the whole mole fraction range at T = 298.15 K. Based on the obtained data, the effect of substituting methyl groups at the nitrogen atom in formamide on the preferential solvation of 1,4-dioxane has been analyzed. A simple model has been proposed to describe the influence of structural and energetic properties of the mixed solvent on the energetic effect of hydrophobic hydration and preferential solvation of 1,4-dioxane by the components of the examined mixture.
The standard enthalpy of combustion of 1,7,7-trimethylbicyclo[2.2.1]heptan-2-one (camphor) has been measured in two aneroid static-bomb combustion calorimeters. The value ΔHo(C10H16O, c) = −(1410.7 ± 0.6) kcalth mol−1 yields the standard enthalpy of formation ΔHfo(C10H16O, c) = −(76.3 ± 0.6) kcalth mol−1. The standard enthalpy of sublimation has been calculated as ΔHs(C10H16O, 298.15 K) = (12.4 ± 0.2) kcalth mol−1. The corresponding gas-phase enthalpy of formation is ΔHo(C10H16O, g) = −(63.9 ± 0.7) kcalth mol−1.
The speed of sound in gaseous methanol has been obtained at 12 temperatures between 260 K and 360 K at pressures in the range 1.03 kPa to 80.5 kPa from measurements of the frequencies of the radial acoustic modes of a spherioal cavity. Perfect-gas heat capacities and second acoustic virial coefficients have been determined from the results. The heat capacities at temperatures between 280 K and 320 K lie about 0.002 · Cpgp, m above those calculated from spectroscopic information, while at 360 K, the worst case, the difference is 0.01 · Cpgp, m. Second virial coefficients of the equation of state have been calculated from the acoustic virial coefficients. These values are compared with values reported in the literature.
Speeds of sound for nitrogen gas have been measured at pressures from 0.03 to 1.5 MPa on 16 isotherms from 80 to 350 K. Measurements were made in a fixed-path acoustic cavity using variable-frequency electrostatic transducers operating between 1 and 30 kHz. Correction for boundary-layer effects were made using existing values of thermodynamic properties.
The compressions of binary mixtures of water + methanol, + ethanol, + i-propanol, and + t-butanol have been measured as a function of composition at 298.15 K and 1000 atm. The partial molar volumes of the components at 1 and 1000 atm have been calculated by combination of the experimental values with available densities at 1 atm for each system. The composition dependence of the compressions is explained in terms of the partial compressions of the components.
The heat capacities of FeS and Fe7S8 have been measured by adiabatic-shield calorimetry at temperatures T from 298.15 K to 1000 K. In addition, heat capacities of Fe0.98S and Fe0.89S have been determined from T = 298.15 K to about 800 K and 650 K, respectively. All compounds crystallize in (NiAs or Cd(OH)2)-related types of structure, and they all exhibit transitions due to disappearance of the lower-temperature antiferromagnetic or ferrimagnetic phase. The Néel temperature is near 590 K for all four samples. FeS shows two additional transitions with heat-capacity maxima at T = 419.6 K and 440 K. The lower-temperature transition originates from structural changes, whereas the higher one is mainly of magnetic origin. For Fe0.98S only one additional transition takes place, with maximum heat capacity at T = 405 K. So also for Fe0.89S, which exhibits a transition 30 K below the Néel temperature. The maximum heat capacity at T = 560 K is due to a structural transition coupled to a magnetic-order-to-order transition. The structural-order-to-disorder transition and the magnetic one overlap in Fe7S8, giving rise to one heat-capacity peak only in the Néel-temperature region. In addition, a smaller effect, related to a phase reaction, is observed in the range T = 650 K to 760 K. The thermodynamic properties and the formation functions are evaluated and discussed.
Low-temperature heat capacities at temperatures from 5 K to 370 K by adiabatic calorimetry and high-temperature enthalpy increments above 450 K to 800 K by drop calorimetry of Li2ZrO3 and Li8ZrO6 have been measured. From the results, smoothed thermochemical and thermophysical functions have been tabulated at selected temperatures up to 1000 K. For the standard molar entropies of Li2ZrO3 and Li8ZrO6 at T = 298.15 K the values S°m/R = (12.79 ± 0.26) and (26.66 ± 0.53), respectively, have been found.
A magnetic suspension densimeter has been used to determine orthobaric liquid densities of gravimetrically prepared binary mixtures of the major components of liquefied natural gas (LNG) i.e. nitrogen, methane, ethane, propane, i-butane, and n-butane, generally between 105 and 140 K. All binary combinations were included in this study, with the exception of nitrogen + i-butane and nitrogen + n-butane. Uncertainties in the reported liquid-mixture densities are discussed in detail. Comparisons are made between excess volumes computed from the present results and comparable values from the literature. It was found that the volumetric properties of binary liquid mixtures of the heavy hydrocarbons (those mixtures not containing nitrogen or methane) are closely approximated by ideal mixing. Some observations are included on the use of excess volumes of the heavy hydrocarbon systems to determine effective molar volumes of n-butane in liquid mixtures below its triple-point temperature. For mixtures containing nitrogen or methane, approximate total vapor pressures are given.
Top-cited authors
Manuel J S Monte
  • University of Porto
Zhao Hongkun
  • Yangzhou University
Hiroshi Suga
  • Osaka University, Japan Toyonaka
Urszula Domańska
  • Warsaw University of Technology
Kenneth N. Marsh
  • University of Western Australia