Nasiru M. Tukur

Hard-sphere mixture excess free energy at infinite size ratio

This article presents the exact limiting value of the derivative of the excess Helmholtz energy, AE, with respect to molecular size at constant temperature, density and composition for a binary mixture of hard spheres with an infinite size ratio (σ11/σ22→∞); i.e., limσ22→0[(∂AhsE/RT)/∂σ22]T,ρ,x,σ11=(π/2)ρx1x2σ112/(1−(π/6)ρx1σ113). This limiting value is compared with the Mansoori–Carnahan–Starling–Leland (MCSL) and also used to test the limits of some commonly used models in estimating the excess free energy of solvents in mixtures or polymer solutions. The models evaluated include the van Laar, Wilson, Edmond–Ogston, Flory–Huggins, Lacome–Sanchez, Scott–Magat, and Chen et al. It is shown that while the MCSL equation of state produces the same limiting value as the exact value reported here the other mixture models deviate from the exact value. This expression may be utilized to correct the mixture theories at their infinite size ratio limits.

Densities and excess volumes of the benzene-cyclohexane system between 298.15 and 473.15 k

Abstract Beg, S.A., Tukur, N.M., Al-Harbi, D.K. and Hamad, E., 1994. Densities and excess volumes of the benzene-cyclohexane system between 298.15 and 473.15 K. Fluid Phase Equilibria, 94: 289-300. This paper reports the results of measurements of the densities of binary mixtures of benzene with cyclohexane using a high pressure stainless steel pycnometer system for the whole composition range at various temperatures between 298.15 and 473.15 K. The experimental densities were compared with those predicted by the Hankison-Brobst-Thomson (HBT) correlation and the Spencer and Danner Modified Rackett (SDR) equation. Both the HBT and the SDR showed an average deviation of about 0.58%. The excess molar volumes, VE, calculated from the density values have been found to be positive for all the concentrations and temperatures considered.

Densities and excess volumes of cyclohexane + hexane between 298.15 K and 473.15 K

Abstract This paper reports the results of measurements of the densities of binary mixtures of cyclohexane with hexane using a high pressure stainless steel pycnometer system at various temperatures between 298.15 K and 473.15 K. The results were compared with those predicted by the Hankinson-Brobst-Thomson correlation (HBT) and the Spencer and Danner modified Rackett equation (SDR). The HBT equation showed an average deviation of about 0.36% from the experimental results while the SDR equation showed a 0.15% average absolute deviation. The excess molar volumes, VE, calculated from the density values have been found to change from positive to negative values with the increase of temperature.

Densities of ternary mixtures of benzene + cyclohexane + hexane between 298.15 and 473.15 K

The results of measurements of the densities of the ternary mixtures of benzene + cyclohexane + hexane using a high pressure stainless steel pycnometer system in the whole composition range over a wide variation of temperature from 298.15 to 473.15 K are presented. The experimental densities were compared with those predicted by the Spencer-Danner-modified Rackett equation (SDR) and the Hankinson-Brobst-Thompson correlation (HBT). The SDR showed an average absolute deviation of 0.33% while the HBT predicted the densities of the mixtures with an average absolute deviation of 0.75%.

SOLUBILITY STUDIES OF PARAFFIN WAXES IN SELECTED PETROLEUM FRACTIONS AND TOLUENE

ABSTRACT Solubility studies of paraffin waxes with melting point range of 43°C to 57°C in two undefined petroleum fractions and Toluene have been carried out. An Attempt was made to develop a correlation for predicting the solubility of the waxes in these solvents. The one parameter ideal solubility law expression has been successfully used to represent the experimental data.