Aim/Objective
1.
To understand the system that involves
three components.
2.
To identify how solubility gets affected
by addition of third component.
3. To learn the rules relating to triangular diagrams.
3. To learn the rules relating to triangular diagrams.
Introduction
In
a three-component system, the concentration of the component can be represented
in the coordinate form. The degree of freedom defined in the system is four
which include temperature, pressure and the concentration of two of the three
components. The concentration of the third component can be obtained by
subtracting the sum of the two of the three components from the total
concentration of the system. When discussing on the three-component system, the
concentrations of the components are expressed according to the weight basis.
When a new component is added to a system containing two components which are
miscible, the solubility of the system will be affected. If the third component
is more soluble in either one of the two components, the solubility of the
system will decrease. The solubility will only increase if the third component
added is soluble in both components at the same time.
Rules Relating
to Triangular Diagrams
1.
100%
by weight of one component is represented by each of the three apexes of the
triangle. The same apex will express the 0% of the other two components.
2.
Lines
AB, BC and CA show the combinations of two-component mixtures of A and B, B and
C, and C and A, respectively.
3.
All
possible combinations of A, B and C are represented by the area within the
triangle.
4.
If
a line is drawn through any apex to a point on the opposite side, the two
components represented by points on such a line are said to be in constant
ratio.
5.
If
a line is drawn parallel to one side of the triangle, it is said that the
proportion of one component is constant whereas the other two components vary
in concentrations.
Apparatus
and Materials
·
Burette
·
Beaker
·
Measuring
cylinder
·
Retort
stand and clamp
·
Toluene
·
Ethanol
·
Distilled
water
Procedure
1.
Mixures
of ethanol and toluene containing the following percentages of ethanol (in
percent) : 10, 25, 35, 50, 65, 75, 90 and 95 were prepared in sealed containers
measuring 100 cm³.
2.
20
ml of each mixture was prepared by filling a certain volume using a burette (accurately).
3.
Each
mixture was titrated with water until cloudiness is observed due to the
existence of a second phase.
4.
A
little water was added and the mixture was shaken well after each addition.
5.
The
experiment was repeated. Average values were determined.
6.
The
room temperature was measured. The percentage was calculated based on the
volume of each component when the second phase starts to appear/separate.
7.
The
points were plotted onto a triangular paper to give a triple phase diagram at
the recorded temperature.
Result
Ethanol (mL)
|
2
|
5
|
7
|
10
|
13
|
15
|
18
|
19
|
Toluene (mL)
|
18
|
15
|
13
|
10
|
7
|
5
|
2
|
1
|
Average Water
(mL)
|
0.4
|
0.6
|
1.0
|
1.7
|
3.3
|
4.7
|
11.4
|
22.2
|
Ethanol (%)
|
10
|
24
|
33
|
46
|
57
|
61
|
58
|
45
|
Toluene (%)
|
88
|
73
|
62
|
46
|
30
|
20
|
6
|
2
|
Average Water
(%)
|
2
|
3
|
5
|
8
|
13
|
19
|
36
|
53
|
Diagram 1
Discussion
In this experiment, we are going to discuss on the
properties of the system containing three-component that exist in one phase
only.
F = C - P + 2
F = 3 - 1 + 2 = 4
where ;
F - Degrees of freedom
C- The number of components
P - The number of phases present
The four degrees of
freedom are temperature, pressure, and the concentrations of two of the three
components. The three components used are Ethanol, Toluene and water. A
three-component system can be explained by referring to the phase diagram as
plotted in Figure 1. This system occurs at constant temperature and pressure. The
compositions of the components are expressed in the form of coordinate for a
triangular-diagram.
Based on the diagram, each of the corners or apexes of
the triangle represents 100% by weight of
component ( A=Ethanol, B= Toluene, C= Water). The same apex will
represents 0% of the other two components. ( A= 0% of Toluene and Water, B= 0%
of Ethanol and Water, C= 0% of Ethanol and Toluene).
As we move along Ethanol-Toluene in the direction of Toluene, the systems of Ethanol and Toluene containing increasing
concentrations of Toluene and
corresponding smaller amounts of Ethanol. Moving along Toluene-Water towards
Water will represent systems of Toluene and Water containing more
concentrations of Water and closer the closer approached Ethanol on the line
Water-Ethanol, the greater will be the concentration of Ethanol in system
of Ethanol and Water.
The area within the triangle represents all the possible
combination of Ethanol, Toluene and Water to give three-component systems. At
points M, its represents the system
contain 10% of Ethanol, 88% of Toluene and 2% of water. The another point R represents 61% of Ethanol,
20% of Toluene and 19% of water. Any line that parallel to one side of the
triangle represents ternary systems in which the proportion of one component is
constant.
There are some error while doing this experiment.
Generally, there are two kind of errors that usually been done during
experiment which are random errors and systemic errors. The common error is the
parallax error. The eye is not put perpendicular to the miniscus of the liquid
correctly. The temperature during experiment is not constant.
The precaution steps that should be taken during the
experiment are wear safety goggles, glove and lab coat while conducting the
chemical. The safety glasses of goggles will protect anything from entering
eyes. The lab coat is important to avoid spilling anything on clothes. The glove
can protect our hand from chemical that can cause harm. Avoid parallax error by
placing the eye such that the line of view is perpendicular to the scale read. The
temperature while doing the experiment should be constant.
Practice
1.
Does the mixture containing 70% ethanol, 20% water and 10% toluene (volume)
appear clear or does it form two layers?
The mixture will appear
clear which is contain one liquid phase and only one layer will be formed.
2.
What will happen if you dilute 1 part of the mixture with 4 parts of (a) water
(b) toluene (c) ethanol?
a)
Two phases will form
b)
Two phases will form
c)
One phase will form
Conclusion
1.
A
three-component system can be explained using a triangular diagram.
2.
The
addition of the third component will affect the solubility of the system. The
solubility of the system will depend on the solubility of the third component
in the other two components.
3.
There
are several rules applied when discussing about the triangular diagrams.
References
1. Patrick J. S, Martin’s Physical Pharmacy and Pharmaceutical Sciences, 50th Edition, 2011, Lippincott Williams & Wilkins
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