PRACTICAL 1 : PHASE DIAGRAM
PART A :
Determination
of Phase Diagram for Ethanol/ Toluene/ Water System Theory
Three-Component
SystemsOBJECTIVE :
- To become familiar with certain rules that relate to the use of triangular coordinates to know the mutual solubility of liquids in a two phase system.\
- Determination of the solubility limits in a ternary system of water and two other liquids (ethanol and toluene), one of which is completely miscible (ethanol) and the other is partly miscible with water (toluene).
- Construction of the solubility curve of the system being studied on triangular diagram.
INTRODUCTION :
Figure 1: Ternary Phase Diagram
In
the diagram above, each corner of the triangular diagram represents a
pure component, which is 100% A, 100%B, 100%C. Meanwhile, each side
represents two-component mixtures and within the triangular diagram
itself represents ternary components. Any line parallel to a side of the
triangular diagram shows constant percentage value for a component, for
example: DE shows 20% of A with varying amounts of B and C. So does
line FG, showing all mixtures containing 50% of B. These lines intercept
with each other at K, which definitely contains 20%A, 50%B as well as
30%C.
Measurements
can be made this way because in a triangular diagram, the sum of all
distances from K which is drawn parallel to the three sides of the
diagram is same and equals to the length of any one side of the
triangular diagram.
The
addition of a third component to a pair of miscible liquids can change
their mutual solubility. If this third component is more soluble in one
of two different components the mutual solubility of the liquid pair is
decreased. However, if it is soluble in both of the liquids, the mutual
solubility is increased. Thus, when ethanol is added to a mixture of
benzene and water, the mutual solubility of the liquid pair increased
until it reached a point whereby the mixture becomes homogenous. This
approach is used in the formulation of solutions.
APPARATUS:
Burette, conical flask, retort stand, measuring cylinder, test tubes
MATERIALS:
Ethanol, toluene, distilled water
PROCEDURES:
Each determination in this experiment is done twice. Mixtures of ethanol and toluene was prepared in a sealed container measuring 100cm3 containing the following percentage of ethanol (in percent) : 10,25,35,50,65,75,90 and 95. 20ml of each mixture was prepared by filling a certain volume using a burette(accurately). Each mixture was titrated with water until cloudiness was observed due to the existence of a second phase. A little water was added and after each addition it was shaken. The room temperature was measured. The percentage based on the volume of each component was calculated when the second phase starts to appear/separate. Points were plotted onto a triangular paper to give a triple phase diagram at the recorded temperature.
RESULTS :
The cloudiness observed.
TRIANGULAR DIAGRAM :
QUESTIONS :
1. Does the mixture containing 70% ethanol, 20% water and 10% toluene (volume) appear clear or does it form two layers?
It appear as a clear solution.
2.What will happen if you dilute one part of the mixture with four parts of water, toluene, and ethanol?
(a). Water : Two phase is formed.
(b). Toluene : Two phase is formed.
(c). Ethanol : The phase remains clear.
DISCUSSION :
Toluene is soluble in ethanol while it is not soluble with water. But, as these three component were mixed until certain proportion, all three components would be completely miscible. This experiment is carried out by first making a solution of ethanol and toluene which will be completely miscible and addition of water where at first it will make up two phase. As we continue to add more water until appropriate amount, it will result to one phase system.
Addition of water to the mixture of ethanol and toluene increases the mutual solubility of the liquid pair until at one point the mixture become homogenous. The region under the graph shows that there are two phase system form which consist of water and toluene since the solubility of water with toluene is weaker than that with ethanol. Meanwhile the region above the graph shows homogenous mixture.
The predicted graph for this experiment.
The are some error when conducting this experiment such as the cloudiness obtained is not correctly observed and the shaking of the test tube was too vigrous for some test tube until it affects the cloudiness of the solution. Some of the precaution taken in this experiment is that parallax error was avoided by placing the eye perpendicularly to the scale of the burette. Besides that , all the glassware was rinsed with water to remove impurities except conical flask as the presence of water before addition of chemicals will affect the experiment.
CONCLUSION :
Incomplete binomial curve was obtained from our experiment due to some errors while conducting this experiment.
REFERENCES :
1. Martin's Physical Pharmacy and Pharmacautical Science, Sixth Edition, Patrick J. Sinko, Wolters Kluwer, Lippincott Williams & Wilkins.
2. "Ternary Phase Diagram" (http://www.sv.vt.edu/classes/MSE2094_NoteBook/96ClassProj/experimental/ternary2.html)
3.Aulton's Pharmaceutics The Design and Manufacture of Medicines, Fourth Edition, Michael E.Aulton, Kevin M.G. Taylor.
RESULTS :
Test tube
|
A
|
B
|
C
|
D
|
E
|
F
|
G
|
H
|
First titration (ml)
|
1.7
|
0.7
|
1.0
|
1.5
|
2.7
|
3.9
|
10.1
|
15.3
|
Second titration (ml)
|
1.7
|
0.7
|
1.0
|
1.5
|
2.6
|
3.8
|
10.0
|
14.8
|
Average volume(ml )
|
1.70
|
0.70
|
0.95
|
1.50
|
2.65
|
3.85
|
10.05
|
15.05
|
Test tube
|
% Ethanol (v/v)
|
Total volume (average v + 20.0ml)
|
Ethanol
|
Toluene
|
Water
|
|||
Volume(ml)
|
Percentage volume(%)
|
Volume(ml)
|
Percentage volume(%)
|
Volume(ml)
|
Percentage volume(%)
|
|||
A
|
10
|
21.70
|
2.00
|
9.22
|
18.00
|
82.95
|
1.70
|
7.83
|
B
|
25
|
20.70
|
5.00
|
24.15
|
15.00
|
72.46
|
0.70
|
3.39
|
C
|
35
|
20.95
|
7.00
|
33.41
|
13.00
|
62.05
|
0.95
|
4.54
|
D
|
50
|
21.50
|
10.00
|
46.51
|
10.00
|
46.51
|
1.50
|
6.98
|
E
|
65
|
22.65
|
13.00
|
57.40
|
7.00
|
30.91
|
2.65
|
11.69
|
F
|
75
|
23.85
|
15.00
|
62.89
|
5.00
|
20.96
|
3.85
|
16.15
|
G
|
90
|
30.05
|
18.00
|
59.90
|
2.00
|
6.66
|
10.05
|
33.44
|
H
|
95
|
35.05
|
19.00
|
54.21
|
1.00
|
2.85
|
15.05
|
42.94
|
TRIANGULAR DIAGRAM :
QUESTIONS :1. Does the mixture containing 70% ethanol, 20% water and 10% toluene (volume) appear clear or does it form two layers?
It appear as a clear solution.
2.What will happen if you dilute one part of the mixture with four parts of water, toluene, and ethanol?
(a). Water : Two phase is formed.
(b). Toluene : Two phase is formed.
(c). Ethanol : The phase remains clear.
DISCUSSION :
Toluene is soluble in ethanol while it is not soluble with water. But, as these three component were mixed until certain proportion, all three components would be completely miscible. This experiment is carried out by first making a solution of ethanol and toluene which will be completely miscible and addition of water where at first it will make up two phase. As we continue to add more water until appropriate amount, it will result to one phase system.
Addition of water to the mixture of ethanol and toluene increases the mutual solubility of the liquid pair until at one point the mixture become homogenous. The region under the graph shows that there are two phase system form which consist of water and toluene since the solubility of water with toluene is weaker than that with ethanol. Meanwhile the region above the graph shows homogenous mixture.
The predicted graph for this experiment.
The are some error when conducting this experiment such as the cloudiness obtained is not correctly observed and the shaking of the test tube was too vigrous for some test tube until it affects the cloudiness of the solution. Some of the precaution taken in this experiment is that parallax error was avoided by placing the eye perpendicularly to the scale of the burette. Besides that , all the glassware was rinsed with water to remove impurities except conical flask as the presence of water before addition of chemicals will affect the experiment.
CONCLUSION :
Incomplete binomial curve was obtained from our experiment due to some errors while conducting this experiment.
REFERENCES :
1. Martin's Physical Pharmacy and Pharmacautical Science, Sixth Edition, Patrick J. Sinko, Wolters Kluwer, Lippincott Williams & Wilkins.
2. "Ternary Phase Diagram" (http://www.sv.vt.edu/classes/MSE2094_NoteBook/96ClassProj/experimental/ternary2.html)
3.Aulton's Pharmaceutics The Design and Manufacture of Medicines, Fourth Edition, Michael E.Aulton, Kevin M.G. Taylor.
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