J.B. Ott

Excess enthalpies for (ethanol + water) at 298.15 K and pressures of 0.4, 5, 10, and 15 MPa

Abstract The design and construction of a modified isothermal-flow calorimeter with a reproducibility of better than 0.5 per cent is described. This apparatus was used to measure H m E for (ethanol + water) at 298.15 K and pressures of 0.4, 5, 10, and 15 MPa. The 0.4 MPa values are in excellent agreement with published values at atmospheric pressure. A fitting equation was developed which gives a good fit of the H m E results over the composition and pressure ranges investigated. We propose that H m E measurements be made on (ethanol + water) at high temperatures and pressures to establish it as a reference system for testing calorimeters. Agreement of our results with existing literature values suggests that it could now be used for this purpose at 298.15 K and atmospheric pressure.

Excess enthalpies, excess volumes, and excess Gibbs free energies for (n-hexane + n-undecane) at 298.15 and 308.15 K

Excess enthalpies, excess volumes, and excess Gibbs free energies are reported over the entire composition range for n-hexane + n-undecane at 298.15 and 308.15 K. HE was obtained with an isothermal mercury-displacement calorimeter, VE with a continuous dilution dilatometer, and GE is calculated from vapor-pressure measurements made with a continuous-dilution vaporpressure apparatus.

Excess enthalpies of (ethanol+water) at 323.15, 333.15, 348.15, and 373.15 K and from 0.4 to 15 MPa

Abstract We report accurate measurements of H m E for (ethanol + water) at 323.15, 333.15, 348.15, and 373.15 K and from 0.4 to 15 MPa with our new high-temperature and high-pressure flow calorimeter. Results at 333.15 K and 0.4 MPa indicate that the mixture has an interesting double minimum with H m E changing sign twice. We recommend that (ethanol + water) be developed as a reference mixture for testing flow calorimeters at high temperatures and pressures.

Excess enthalpies, excess Gibbs free energies, and excess volumes for (cyclohexane + n-hexane), and excess Gibbs free energies and excess volumes for (cyclohexane + methylcyclohexane) at 298.15 and 308.15 K

Excess enthalpies, excess volumes, and excess Gibbs free energies are reported over the entire composition range for (methylcyclohexane + n -hexane) at 298.15 and 308.15 K. Excess Gibbs free energies and excess volumes are reported over the entire composition range for (cyclohexane + n -hexane) at the same temperatures. H E was obtained with an isothermal mercury-displacement calorimeter, V E was obtained with a continuous-dilution dilatometer, and G E was calculated from vapor pressures measured with a continuous-dilution apparatus.

Determination of excess volumes in cyclohexane + benzene and + n-hexane with a vibrating-tube densimeter

Abstract Excess volumes have been measured by means of a vibrating-tube densimeter for cyclohexane + benzene at 298.15 K, and cyclohexane + n -hexane at 283.15, 298.15, and 313.15 K. The pressure coefficient of the excess enthalpy was calculated from the excess volumes of cyclohexane + n -hexane, and compared with directly measured enthalpies. The two sets of results are in good agreement.

Excess enthalpies for (ethanol + water) at 398.15, 423.15, 448.15, and 473.15 K and at pressures of 5 and 15 MPa. Recommendations for choosing (ethanol + water) as an HmE reference mixture

Abstract We report accurate measurements of H m E { x C 2 H 5 OH + (1 − x )H 2 O} at 398.15, 423.15, 448.15, and 473.15 K and at 5 and 15 MPa. This completes our study of this mixture at 25 K temperature intervals from 298.15 to 473.15 K. We propose { x C 2 H 5 OH + (1 − x )H 2 O} as a reference mixture for testing mixing calorimeters. The arguments are as follows. The chemicals are inexpensive, stable, easily purified, non-toxic, and easily disposed of; H m E is relatively insensitive to impurities; H m E is reasonably well behaved as a function of pressure and temperature; and H m E can be accurately represented as a function of x by an equation.

Excess volumes of n-hexane +n-heptane, +n-octane, +n-nonane, and +n-decane at 283.15, 298.15, and 313.15 K

Abstract Excess volumes V E have been measured by the use of a vibrating-tube densimeter for n -hexane+ n -heptane, + n -octane, + n -nonane, + n -decane at 283.15, 198.15, and 313.15 K. The V E s are negative, and become systematically more negative as either the temperature or the size of the molecules increases. The V E ( x ) become less symmetrical about x = 0.5 as the size of the molecules increases. These results are in sharp contrast to the analogous results for (cyclohexane + n -alkane).

Excess enthalpies, excess volumes, and excess Gibbs free energies for n-hexane + di-n-butyl ether at 298.15 and 308.15 K

Abstract Excess enthalpies, excess volumes, and excess Gibbs free energies are reported over the entire composition range for n -hexane + di- n -butyl ether at 298.15 and 308.15 K. H E was obtained with an isothermal mercury displacement calorimeter, V E with a continuous dilution dilatometer, and G E is calculated from vapor-pressure measurements made with a continuous-dilution vapor-pressure apparatus.

Excess enthalpies, excess Gibbs free energies, and excess volumes for (di-n-butyl ether + benzene) and excess Gibbs free energies and excess volumes for (di-n-butyl ether + tetrachloromethane) at 298.15 and 308.15 K

Abstract Excess enthalpies H E , excess volumes V E , and excess Gibbs free energies G E are reported over the entire composition range for di- n -butyl ether + benzene at 298.15 and 308.15 K. G E s and V E s are reported over the entire composition range for di- n -butyl ether + tetrachloromethane at the same temperatures. V E was obtained with a continuous dilution dilatometer, H E with an isothermal mercury-displacement calorimeter, and G E was calculated from vapor-pressure measurements made with a continuous-dilution apparatus.

Enthalpies of formation of molecular addition compounds in tetrachloromethane + p-xylene, + toluene, and + benzene from (solid + liquid) phase equilibria

Abstract A detailed (solid + liquid) phase diagram for (tetrachloromethane + p -xylene) has been obtained from time-against-temperature warming curves. The standard molar enthalpies of formation of the 1-1 intermolecular compounds in tetrachloromethane + benzene, + toluene, and + p -xylene have been calculated from the corresponding (solid + liquid) equilibria.