Physical Processes - Isoconversional Kinetics of Thermally Stimulated Processes - page 125

Fig. 3.53 Phase diagram
for a solid-liquid system.
The solid line represents the
temperature at which solid
and liquid can coexist at
equilibrium

one phase

two phases

T=T 1

T=T 2

x

uid B dissolved in liquid A is seen in Fig. 3.54 . The solid line bell curve tracks the
temperatures at which a solution forms two phases of different concentration that
can coexist in equilibrium. The ascending wing of the curve reflects an increase in
the solubility of B as a function of temperature. The trend is similar to that seen in
Fig. 3.53 . The trend continues until reaching the critical temperature, T c , above which
both liquids become infinitely soluble in each other. The descending wing of the curve
corresponds to the solubility of A in B. When the fraction of B becomes larger than
that of A, B turns from solute to solvent. Thus, this wing represents an increase in the
solubility of A as a function of temperature. If a solution of the concentration x B1 pre-
pared at the temperature T 1 , which is above the respective equilibrium temperature,
it will exist as a single-phase system. Decreasing the solution temperature to the tem-

Fig. 3.54 Phase diagram
for a liquid-liquid system.
The solid line represents the
temperature at which two
liquid phases of different
composition can coexist at
equilibrium. The dash-dot
line is the spinodal line