1070-4272/01/7412-1997 $25.00 C 2001 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 74, No. 12, 2001, pp. 1997!2001. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 12, 2001,
Original Russian Text Copyright + 2001 by A. Rasulov, S. Rasulov.
OF SYSTEMS AND PROCESSES
Liquid!Liquid and Liquid!Vapor Phase Equilibria
in Stratifying Binary System n-Hexane!Water
A. R. Rasulov and S. M. Rasulov
Institute of Physics, Daghestan Scientific Center, Russian Academy of Sciences, Makhachkala, Daghestan, Russia
Received October 5, 2000; in final form, April 2001
Abstract-Thermal properties of a binary system n-hexane3water were studied by the constant-volume-
piezometer method for seven concentrations of water on the basis of isochores at temperatures of 372.753
620.55 K, homogeneous phase densities in the range 66.873834.30 kg m
, and pressures of up to
Studying the thermal properties on n-alkane3water
mixtures is of not only theoretical, but also practical
interest, since natural hydrocarbon mixtures are, as
a rule, in contact with water. In addition, stratifying
water3hydrocarbon systems are widely used in chem-
ical technology, petroleum and petrochemical indus-
tries, and power engineering.
The properties (PVT) of the n-hexane3water binary
system, which can be considered a simple model of
a stratal mixture, were studied in a number of works
. However, data on phase liquid3liquid and
liquid3vapor equilibria are scarce.
In this work, thermal properties of the n-hexane3
water binary system was studied by the constant-
volume piezometer method at temperatures of 372.753
620.55 K, homogeneous phase densities r of 66.873
834.30 kg m
, and pressures of up to 65.34 MPa for
seven concentrations x of water (mol fraction): 0.166,
0.257, 0.347, 0.615, 0.827, 0.935, and 0.964. The
measurements cover a parameter range between the
liquid3liquid and liquid3vapor phase equilibria.
The temperature of the system was maintained au-
tomatically within +0.01 K by means of three heat
controllers. The pressure was controlled using a
membrane transducer with sensitivity of 0.005 MPa
and measured with standard pressure-gage at pressures
below 1 MPa and MP-600 deadweight gage with ac-
curacy of 0.05% at pressures exceeding 1 MPa. The
piezometer volume (21.160 + 0.025 cm
) was deter-
mined by calibration against water. The piezometer
was filled under vacuum through a valve at the pie-
zometer edge. Mixtures were prepared using degassed
twice-distilled water and n-hexane of 99.94% purity.
The mixture components were weighed on analytical
balance with an error not exceeding 0.5 mg. The error
in density measurements was 0.1230.15%. The setup
was described in detail in .
The measurements were made using isochores.
For each composition, 739 isochores were obtained,
which covered a wide range of densities. The depen-
dences of pressure P on temperature T along the iso-
chores exhibit inflections corresponding to liquid3
liquid and liquid3vapor phase transitions. A typical
P3T dependence along different isochores for a com-
position with x = 0.935 is given in Fig. 1. Lines con-
necting the inflection points are phase equilibrium
Fig. 1. Dependence of P on temperature T for n-hexane3
water binary system of composition x = 0.935 along iso-
chores. r (kg m
): (1) 205.1, (2) 273.4, (3) 341.7,
(4) 410.1, (5) 478.4, (6) 546.8, (7) 615.1, and (8) 649.3.