1070-4272/05/7803-0390C2005 Pleiades Publishing, Inc.
Russian Journal of Applied Chemistry, Vol. 78, No. 3, 2005, pp. 390!393. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 3,
2005, pp. 394!397
Original Russian Text Copyright + 2005 by Sinegubova, Il’in, Cherkasov.
OF SYSTEMS AND PROCESSES
Mutual Solubility of Components and Critical Solution Points
in the System Water3Isopropyl Alcohol3n-Dodecane
in the Temperature Range 53120oC
S. I. Sinegubova, K. K. Il’in, and D. G. Cherkasov
Chernyshevskii Saratov State University, Saratov, Russia
Received June 30, 2004
Abstract-The mutual solubility of components and critical solution points in the ternary system water3
isopropyl alcohol3n-dodecane were studied by a visual-polythermal technique at saturated vapor pressure
in the temperature range 53120 oC. The mixture composition in the critical solution point was studied in
relation to temperature.
The mutual solubility of components in ternary
systems water3aliphatic alcohol3n-alkane was studied
by numerous researchers. In , the mutual solubility
of components in 19 ternary systems was analyzed in
relation to the molecular structure of particular com-
ponents and features of intermolecular interactions.
The isothermal and polythermal solubility diagrams of
several systems of this kind were studied in detail
in . It was shown in these papers that the critical
solution point is an important characteristic of the
phase diagram, because its location reflects the mutual
solubility of components and their interaction in the
system. Therefore, in studying the mutual solubility
of liquid compounds, the location of the critical solu-
tion point in the phase diagram and factors influenc-
ing the system composition in this point should be
determined. The temperature effect on the mixture
composition in the critical solution point at a constant
pressure was studied only for a few ternary systems
and in a narrow temperature range.
In this study we examined the influence of tem-
perature on the mutual solubility of components and
the composition of the critical point in the system
water3isopropyl alcohol3n-dodecane at saturated
vapor pressure in the temperature range 53120oC.
This system was not studied previously.
All the compounds used in our experiments were
thoroughly purified. Water was purified on a DEM-20
MERA-POLNA double-distiller. The initial isopropyl
alcohol (chemically pure grade) containing 99.8%
main compound was dried over calcined K
a day, decanted, and then distilled on a 0.3-m Vigreux
column, and the fraction with bp 82.2382.4oC was
collected. The purified isopropyl alcohol was stored
over molecular sieves (4 A). n-Dodecane (chemically
pure grade) was dried over molecular sieves (4 A)
and used without further purification. All the liquids
were identified by their boiling point, refractive index,
and density. These characteristics were in good agree-
ment with the reference data .
The temperature of the phase transition from a two-
phase mixture (l
) to a homogeneous state (l)
= l in the ternary systems was determined in
sealed test tubes by the visual polythermal technique
 with +0.1oC accuracy. The required temperature
was maintained with a Mechanic Medingen U-10
thermostat and was monitored with calibrated decimal
mercury thermometers in the temperature ranges
0350, 503100, and 1003150oC. The relative ac-
curacy of determining the composition of the coexist-
ing equilibrium phases did not exceed +0.5%.
The compositions of the ternary system in the criti-
cal solution points were determined by the phase
volume ratio technique . We chose such composi-
tions of ternary mixtures water3isopropyl alcohol3
n-dodecane at which the mixture exhibited the critical
opalescence in the vicinity of the critical solution
point (+0.1 C) and separated into two liquid phases of
equal volume. The critical behavior of the systems
under consideration was studied in sealed graduated
test tubes. The phase volumes were determined with
an accuracy of about 5%.