Jean-Pierre E. Grolier

n-hexane as a model for compressed simple liquids

Isobaric thermal expansivities, αp, ofn-hexane have been measured by pressure-controlled scanning calorimetry from just above the saturation vapor pressure to 40 MPa at temperatures from 303 to 453 K and to 300 MPa at 503 K. These new data are combined with literature data to obtain a correlation equation for αp valid from 240 to 503 K at pressures up to 700 MPa. Correlation equations are developed for the saturated vapor pressure, specific volume, and isobaric heat capacity of liquid n-hexane from 240 to 503 K. Calculated volumes, isobaric and isochoric specific heat capacities. isothermal compressibilities, and thermal coefficients of pressure are presented for the entire range of pressure and temperature. The pressure-temperature behavior of these quantities is discussed as a model behavior for simple liquids without strong intermolecular interactions.

Thermodynamic properties of binary mixtures containing ketones I. Excess enthalpies of some aliphatic ketones + n-hexane, + benzene, and + tetrachloromethane

Abstract Flow-calorimetric measurements of excess enthalpies at 298.15 K are reported for mixtures of 2-butanone + n -hexane, + benzene, + tetrachloromethane, and of 2-pentanone and 3-pentanone with the same set of second components. The results indicate that important interactions occur between the ketoxy group and benzene and tetrachloromethane.

An isothermal scanning calorimeter controlled by linear pressure variations from 0.1 to 400 MPa. Calibration and comparison with the piezothermal technique

An isothermal scanning calorimeter controlled by linear pressure variations is described for the pressure range 0.1–400 MPa at temperatures from 303 to 573 K. The rate of pressure variations can be as low as 0.002 MPa/s over the whole pressure range. The functioning of the instrument was tested by measuring the coefficient of thermal expansivity of liquid n‐hexane, with calibration performed with gaseous nitrogen and by measuring the coefficient of thermal expansivity of benzene with calibration performed with liquid n‐hexane. The results are compared with literature results obtained by the piezothermal technique and with results obtained in the present instrument by the use of a pressure stepwise scanning mode. An example of an investigation of an isothermal solid‐to‐liquid transition in benzene is also given.

Thermodynamic properties of binary mixtures containing esters. I. Analysis of the properties of n-alkanoate + n-alkane and n-alkanoate + n-alkanoate mixtures in terms of a quasichemical group-contribution model

Abstract The thermodynamic properties of n-alkanoate + n-alkane and + n-alkanoate binary liquid mixtures are examined on the basis of the group-surface interaction version of the Guggenheim-Barker quasichemical pseudolattice theory. All the data available in the literature for liquid—vapor and liquid—liquid equilibria, excess enthalpies and activity coefficients at infinite dilution are taken into consideration. Using only four alkyl-group increments, in addition to the two group-interaction parameters for methyl ethanoate, the model provides a fairly consistent description of the properties of the mixtures as functions of composition, temperature and chain length. The results are discussed in comparison with other classes of systems investigated previously (alkanones and alkanals).

Enthalpies of absorption and solubility of CO2 in aqueous solutions of methyldiethanolamine

Abstract A flow mixing unit using a SETARAM C-80 calorimeter, developed for measuring the enthalpy of solution of two fluids, has been used to measure enthalpies of absorption of carbon dioxide in a 30 wt.% aqueous solution of methyldiethanolamine (MDEA) at three temperatures 313.15, 353.15, 393.15 K and three pressures 2.0, 5.0, 10.0 MPa. We have established that the effect measured by calorimetry corresponds not only to the absorption of CO2 in the aqueous solution but also to the vaporisation of water into the carbon dioxide depending on the temperature and the pressure of the experiment. The enthalpies measured by calorimetry were compared with those calculated from solubility measurements and a reasonable agreement within the accuracy of measurement and calculation was found.

Excess properties of mixtures of some n-alkoxyethanols with organic solvents: III. VE and CEp with butan-1-ol at 298.15 K

The excess molar volumes, VE, and the excess molar heat capacities, CEp are determined as a function of mole fraction, X, at atmospheric pressure and 298.15 K for 2-methoxyethanol (1), 2-ethoxyethanol (1), 2-butoxyethanol (1), 2-(2-methoxyethoxy)ethanol (1), 2-(2-ethoxyethoxy)ethanol (1), 2-(2-butoxyethoxy)ethanol (1) with butan-1-ol (2) mixtures. The VE values decrease in magnitude as the alkyl chain length of the n-alkoxyethanol increases for the two homologous series; they are positive except for the mixtures containing 2-butoxy-ethanol and 2-(2-butoxyethoxy)ethanol for which they are negative over the whole mole-fraction range. The CEp values are positive and relatively small for all the mixtures studied.

Thermodynamics of (a halogenated ethane or ethene + an n-alkane). VE and CPE of mixtures containing either 1,1,2,2-tetrachloroethane or tetrachloroethene

Abstract Excess molar volumes V E and excess molar heat capacities C P E at constant pressure have been determined at 298.15 K as a function of mole fraction x 1 for mixtures belonging to series I: {x 1 1,1,2,2-C 2 H 2 Cl 4 + x 2 n-C n H 2n+2 }, and series II: {x 1 C 2 Cl 4 + x 2 n-C n H 2n+2 }, n = 7 and 14. While 1,1,2,2-tetrachloroethane (1,1,2,2-TCE) exhibits trans-gauche rotational isomerism, tetrachloroethene (TCEe) is a rigid molecule without permanent electric dipole moment. The instruments used were a vibrating-tube densimeter and a Picker flow calorimeter. For series I, V E (x 1 =0.5)/(cm 3 .mol −1 ) = 0.153 for n = 7, and 1.029 for n = 14, as compared to −0.192 for n = 7, and 0.313 for n = 14 in series II. The highly asymmetric shape of V E vs. x 1 of (1,1,2,2-TCE + n-C 7 H 16 ) is noted. For series I, the composition dependence of C P E as well as its dependence on n are similar to those for the series (1,2-dichloroethane + an n-alkane) in that for n = 7 the minimum (−2.18 J.K −1 .mol −1 ) is at x 1,min = 0.364 and a shoulder extends to, roughly, x 1 ≈ 0.75. For n = 14, C P E (x 1,min ) = −4.77 J.K −1 .mol −1 at x 1,min = 0.423, and no shoulder is discernible. The curves C P E vs. x 1 for series II are more or less parabolic, with C P E (x 1,min )/(J.K −1 .mol −1 ) = −0.14 at x 1,min = 0.512 for n = 7, and −1.66 at x 1,min = 0.502 for n = 14.

Thermochemical behaviour of mixtures of n-alcohol + aliphatic ether: heat capacities and volumes at 298.15 K

Abstract Molar excess volumes VE at 298.15 K were obtained as a function of mole fraction for each of the binary mixtures formed from methyl n-butylether, 3,6-dioxaoctane, and 2,5,8-trioxanonane + methanol, and + ethanol, and also for 2,5,8-trioxanonane+1-propanol. In addition, a Picker flow calorimeter was used to determine molar excess heat capacities CPE at 298.15 K for the same mixtures. All the excess heat capacities are positive and the excess volumes are negative. Values of VE of mixtures with a given ether become less negative with increasing chain length of the alcohol.

Thermodynamics of liquid mixtures containing n-alkanes and strongly polar components: VE and C P E of mixtures with either pyridine or piperidine

Excess molar volumes VE and excess molar heat capacities CP/E at constant pressure have been obtained, as a function of mole fraction x1, for several binary liquid mixtures belonging either to series I: pyridine+n-alkane (ClH2l+2), with l=7, 10, 14, 16, or series II: piperidine+n-alkane, with l=7, 8, 10, 12, 14. The instruments used were a vibrating-tube densimeter and a Picker flow microcalorimeter, respectively. VE of pyridine+n-heptane shows a S-shaped composition dependence with a small negative part in the region rich in pyridine (x1>0.90). All the other systems show positive VE only. The excess volumes increase with increasing chain length l of the n-alkane. The excess molar heat capacities of the mixtures belonging to series II are all negative, except for a small positive part for piperidine+n-heptane in the region rich in piperidine (x1>0.87). The CP/E at the respective minima, CP/E(x1,min), become more negative with increasing l, and the x1,min values range from about 0.26 (l=7) to 0.39 (l=14). Most interestingly, mixtures of series I exhibit curves of CP/E against x1 with two minima and one maximum, the so-called W-shape curves.

Heat capacities and densities of mixtures of very polar substances 1. Mixtures containing acetonitrile

Excess molar heat capacities CEp, m at constant pressure and excess molar volumes VEm have been determined, as a function of mole fraction X at 298.15 K and atmospheric pressure for the eight liquid mixtures: {xCH3CN + (1 − x)C6H6}, {xCH3CN + (1 − x)1,4-C4H8O2}, {xCH3CN + (1 − x)N(C2H5)3}, {xCH3CN + (1 − xCHCl3}, {xCH3CN + (1 − x)(CH3)2CHOCH(CH3)2}, {xCH3CN + (1−x)CH3COCH3}, {xCH3CN + (1−x)HCON(CH3)2}, and {xCH3CN + (1 − x)(CH3)2SO}. The dipole moment of acetonitrile is p/(10−30·C·m) = 13.2, while for the second components p/(10−30·C·m) ranges form 0 for benzene to 13.2 for dimethylsulfoxide. The instruments used were a Picker flow microcalorimeter and a vibrating-tube densimeter, respectively. The CE p, ms are negative and small for {xCH3CH + (1−x)1,4-C4H8O2}, {xCH3CN + (1−x)HCON(CH3)2}, and {xCH3CN + (1−x)(CH3)2SO}; S-shaped (and small) for {xCH3CN + (1−x)C6H6} and {xCH3CN + (1−x)CH3COCH3}; and positive and quite large for {xCH3CN + (1−x)(CH3)2CHOCH(CH3)2}, {xCH3CN + (1−x)CHCl3}, and {xCH3CN + (1−x)N(C2H5)3} (at x = 0.5, CEp, m = 6.04 J·K−1·mol−1 for the last mixture). VEm VEm{xCH3CN + (1−x)C6H6} shows an S-shaped composition dependence, with the positive part extending from about x = 0.63 to pure benzene. All the other excess volumes are negative and rather small.