Article

Excess molar volumes and isentropic compressibilities of binary liquid mixtures containing n-alkanes at 298.15 K

Pramana (Impact Factor: 0.72). 10/2002; 59(4):663-670. DOI: 10.1007/s12043-002-0076-6

ABSTRACT Excess molar volumes (V
E) and deviation in isentropic compressibilities (Δβ
s) have been investigated from the density ρ and speed of sound u measurements of six binary liquid mixtures containing n-alkanes over the entire range of composition at 298.15 K. Excess
molar volume exhibits inversion in sign in one binary mixture, i.e., n-heptane + n-hexane. Remaining five binary mixtures,
n-heptane + toluene, cyclohexane + n-heptane, cyclohexane + n-hexane, toluene + n-hexane and n-decane + n-hexane show negative
excess molar volumes over the whole composition range. However, the large negative values of excess molar volume becomes domainant
in toluene + n-hexane mixture. Deviation in isentropic compressibility is negative over the whole range of composition in
the case of all the six binary mixtures. Existence of specific intermolecular interactions in the mixtures has been analyzed
in terms of excess molar volume and deviation in isentropic compressibility.

0 Followers
 · 
226 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This thesis describes the development and testing of two apparatuses; a vibrating wire viscometer to measure the viscosity of fluids over a wide range of temperature and pressure; and a microwave cavity resonator to measure dew points, gas phase densities, and liquid drop out volumes. Viscosity and density of downhole fluids are very important properties as their values can determine the economic viability of a petroleum reservoir. A vibrating wire viscometer has been developed with an electrically insulating tensioning mechanism. It has been used with two wires, of diameters (0.05 and 0.150) mm, to measure the viscosity of methylbenzene and two reference fluids with viscosities of (10 and 100) mPa·s at T = 298 K and p = 0.1 MPa, at temperatures in the range (298 to 373) K and pressures up to 40 MPa, where the viscosity covers the range (0.3 to 100) mPa·s, with a standard uncertainty < 0.6 %. The results differ from literature values by < ±1 %. The results demonstrate that increasing the wire diameter increases the upper operating viscosity range of the vibrating wire viscometer, a result anticipated from the working equations. For the microwave cavity resonator, the method is based on the measurements of the resonance frequency of the lowest order inductive-capacitance mode. The apparatus is capable of operating at temperatures up to 473 K and pressures below 20 MPa. This instrument has been used to measure the dew pressures of {0.4026CH4 + 0.5974C3H8} at a temperature range from 315 K up to the cricondentherm ˜ 340 K. The measured dew pressures differ by less than 0.5 % from values obtained by interpolation of those reported in the literature, which were determined from measurements with experimental techniques that have quite different potential sources of systematic error than the radio-frequency resonator used here. Dew pressures estimated from both NIST 14 and the Peng-Robinson equation of state lie within < ±1 % of the present results at temperature between (315 and 337) K while predictions obtained from the Soave-Redlich-Kwong cubic equation of state deviate from our results by 0.4 % at T = 315 K and these differences increase smoothly with increasing temperature to be -2.4 % at T = 337 K. Densities derived from dielectric permittivity measurements in the gas phase lie within < 0.6 % of the values calculated from the Soave-Redlich-Kwong cubic equation of state and about 1 % from values obtained with the Harvey and Prausnitz correlation based on a mixture reduced density. The calculations with Kiselev and Ely parametric crossover equation of state (based on Patel-Teja EOS) gave deviations < 0.7 %. Liquid volume fractions, in the 2-phase region, were measured from (0.5 to 7) cm3 in a total volume of about 50 cm3 at different isochors. The measured liquid volume fractions differ from values obtained with the Soave-Redlich-Kwong cubic equation of state by between 0 and 3 % at T < 326 K and about 8 % on approach to the critical region. The large deviations observed in the critical region were anticipated because of the known poor performance of the cubic equations of state with regard to the calculation of the liquid density in the vicinity of the critical temperature.
  • [Show abstract] [Hide abstract]
    ABSTRACT: A vibrating wire viscometer has been developed with an electrically insulating tensioning mechanism. It has been used with two wires, one of diameter 0.05 mm the other of diameter 0.15 mm, to measure the viscosity of methylbenzene and two reference fluids with viscosities of (14 and 240) mPa·s at T = 298 K and p = 0.1 MPa at temperatures in the range from (298 to 373) K and pressures below 40 MPa, where the viscosity covers the range from (0.3 to 100) mPa·s with an uncertainty of < 0.6 %. The results so obtained differ from literature values by < 1 %. Measurements with the 0.150 mm diameter wire at T = 301 K demonstrate that the upper operating viscosity is 200 mPa·s with an uncertainty of about 3 %.
    Journal of Chemical & Engineering Data 02/2005; 50(2). DOI:10.1021/je049636m · 2.05 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The densities of the (cyclohexane + pentane, or hexane, or heptane, or octane, or nonane) systems were measured at the temperature 298.15 K by means of a vibrating-tube densimeter. Their respective excess molar volumes were calculated and correlated using the fourth-order Redlich—Kister equation, with the maximum likelihood principle being applied in the determination of the adjustable parameters. The values of excess molar volumes were negative for the cyclohexane + pentane system, whereas they were positive for the other systems with the values increasing with the number of carbon atoms in the respective alkane molecules.
    Chemical Papers- Slovak Academy of Sciences 12/2007; 61(6):497-501. DOI:10.2478/s11696-007-0068-6 · 1.19 Impact Factor

Preview

Download
10 Downloads
Available from