Russian Journal of Applied Chemistry, 2012, Vol. 85, No. 9, pp. 1335−1338.
Pleiades Publishing, Ltd., 2012.
Original Russian Text © E.A. Kazoyan, A.S. Khachatryan, 2012, published in Zhurnal Prikladnoi Khimii, 2012, Vol. 85, No. 9, pp. 1417−1421.
AND CORROSION PROTECTION OF METALS
in the Dimethyl Sulfoxide–Methanol System
E. A. Kazoyan and A. S. Khachatryan
Yerevan State University, Armenia
Received November 9, 2011
Abstract—The liquid–vapor phase equilibrium in the dimethyl sulfoxide–methanol binary system was studied
with the use of a statistical method. Partial pressures of dimethyl sulfoxide and methanol were calculated by inte-
grating the Gibbs–Duhem equation. Molar excess Gibbs energies were described by the Redlich–Kister equation,
and correlation parameters were calculated. It was found that molar excess Gibbs energies are negative, and the
deviation from ideality increases as temperature increases.
The study of liquid–vapor phase equilibria for binary
systems is an important and actual problem of physical
chemistry of solutions. Pressure of saturated vapors being
in equilibrium with a liquid depends on the nature and
temperature of the liquid and gives an information on
intermolecular interactions in it.
The dimethyl sulfoxide–methanol system is interest-
ing owing to the fact that its components are capable to
form hydrogen bonds. The formation of homo- and het-
eroassociates in this system was found both experimen-
tally and by quantum-chemical calculations [1–4]. It is
obvious that the presence of such competing interactions
considerably inﬂ uences the liquid–vapor equilibrium in
Practical importance of studying the liquid–vapor
phase equilibrium of alcohol DMSO solutions is caused
by the fact that DMSO has a wide application both in
biology, and in medicine [5–9]. Dimethyl sulfoxide acts
as a cell cryoprotector capable to penetrate into a living
tissue without causing damages . It is found also that
DMSO is present in small amounts is human blood and
In this work we have measured the total pressure of
saturated vapors of the binary DMSO–MeOH solution
at 298 and 303 K. Partial pressures of the components,
activity coefﬁ cients, and molar excess Gibbs energy were
calculated from the experimental data.
Dimethyl sulfoxide (Aldrich Chemical Co, 99.5%)
was used without further puriﬁ cation. Absolute MeOH
(99.9% purity) was obtained by distilling preliminary
dehydrated methyl alcohol.
Saturated vapor pressures were measured by means
of the Clausius–Clapeyron apparatus (Fig. 1) according
to a technique described in works [10, 11].
The technique of measuring saturated vapor pressures
was the following: the both components of the binary
solution were preliminary degased by means of liquid
nitrogen three times and then mixed in an isoteniscope
under vacuum. Vapor pressures were measured by mer-
cury and oil manometers (Fig. 1). A BM-1 diffusion oil of
the 0.863 g cm
density was used in the oil manometer.
By calculation, 15.7 mm of an oil column corresponds
to 1 mm Hg, i.e. 1 mm of an oil column corresponds to
8.494 Pa. The error of pressure measurement by the oil
manometer is 4 Pa, and the error of measuring tempera-
ture is ±0.02 K.
Saturated vapor pressures were measured both above
pure substances (DMSO, MeOH) and above binary
DMSO–MeOH solutions in the whole concentration
interval at temperatures 298 and 303 K.
Experimental data on the total saturated vapor pressure