ISSN 1070-4272. Russian Journal of Applied Chemistry, 2006, Vol. 79, No. 5, pp. 856 !857. + Pleiades Publishing, Inc., 2006.
Original Russian Text + I.P. Kalinina, 2006, published in Zhurnal Prikladnoi Khimii, 2006, Vol. 79, No. 5, pp. 868!869.
Melting Diagram of the Ternary System
I. P. Kalinina
Samara State Technical University, Samara, Russia
Received February 9, 2005; in final form, December 2005
Abstract-The ternary system cyclohexane3n-hexadecane3n-docosane was studied by low-temperature
differential thermal analysis.
Systems based on paraffin hydrocarbons are of
interest for petroleum chemistry and oil refining.
These hydrocarbons are characterized by chemical
inertness, high stability, and high heats of phase
transitions. However, their studies involve certain
problems. First, the temperature interval of interest is
inconvenient for studies. Second, the phase diagrams
in this case are extremely complex, despite the fact
that the substances constituting the systems do not
react chemically with each other, because in some
cases the systems involve all the existing types of
nonchemical phase equilibria: eutectics, peritectics,
and formation of solid solutions with and without
extrema. Interpretation of the diagrams in the course
of construction is very sophisticated and requires high
In this study we examined the ternary system cy-
clohexane3n-hexadecane3n-docosane by low-tempera-
ture differential thermal analysis (LTDTA) . This
method allows determination of the melting points for
compositions of the system studied and enables con-
struction of its melting diagram.
The cyclohexane3n-hexadecane3n-docosane (C
) system forms three binary sub-
Table 1. Characteristics of binary subsystems of eutectic type
³ Content in eutectic, wt %
³³cyclohexane ³ n-hexadecane ³ n-docosane
Cyclohexane3hexadecane  ³ 12.7 ³ 80.77 ³ 19.23 ³ 3
Cyclohexane3docosane  ³ 4.6 ³ 83.8 ³ 3 ³ 16.2
n-Hexadecane3docosane  ³ 16.2 ³ 3 ³ 94.3 ³ 5.7
systems (cyclohexane3n-hexadecane, cyclohexane3
n-decosane, and n-hexadecane3n-docosane). The char-
acteristics of these subsystems are given in Table 1.
The available data on the binary systems suggest
that the ternary system C
is eutectic; this assumption was confirmed experi-
The polythermal section e
in the crystallization
field of n-C
was chosen in the phase diagram
of the ternary system (see figure). The phase diagram
of this section was constructed from the LTDTA data
and was used for determining the ratio of C
in the ternary eutectic E. The eutectic com-
position of the ternary system determined from the
E6E section (see figure) is as follows
(wt %): C
19.1, and n-C
1.0. The phase diagram of the ternary system cyclo-
hexane3n-hexadecane3n-docosane is characterized
in Table 2.
The specific enthalpy of melting for the eutectic
composition of the ternary system (80 J g
determined by quantitative low-temperature differen-
tial thermal analysis.