1. Three component systems
Physical Pharmacy
Three component systems

2. Phases
A phase is a homogeneous portion of a system Uniform chemical and physical properties
Properties of a material depend on
1. Number of phases present
2. Types of phases present
3. Amount of phases present
4. Distribution of phases present
The properties can be changed by altering these quantities.
In order to make these changes, it is essential to know the condition under these quantities exist and the condition under which a change in phase will occur.

3. Phase diagram
Phase diagram is a type of chart used to show condition at which thermodynamically distinct phases can occur at equilibrium at different temperature, pressure, and composition .
A system reaches equilibrium if its free energy is at minimum.
At equilibrium characteristics of the system do not change with time. i.e it is stable.
Changing temperature or pressure will change the system free energy.

4. Degrees of freedom
Coexistence of phases can only occur over a limited range.
phase rule is a relationship for determining the least number of intensive variables that can be changed without changing the equilibrium state of the system.
P is the number of phases present
C in represents the number of components in the system
F is termed the number of degrees of freedom

5. Phase Equilibria in Three-Component Systems
In systems containing three components but only one phase.
four degrees of freedom are temperature, pressure, and the concentrations of two of the three components.
Only two concentration terms are required because the sum of these subtracted from the total will give the concentration of the third component.
Temperature and pressure are considered to be constant.

7. Ternary diagram
Each corner of triangle represent 100% of one component
The three lines joining the corner points represent two components of three possible combinations
The area within triangle all possible combinations of A,B and C

8. Ternary phase diagram

10. Alterations of the binodal curves with changes in temperature.

11. Solubilization of toluene
Toluene is a clear colorless liquid with a characteristic aromatic odor and insoluble in water.
It can be dissolved in water by using a co-solvent like alcohol.
This is called co-solvency effect and alcohol is called co-solvent.
Alcohol reduces the polarity of water and helps in dissolving toluene in water.

12. The effect of alcohol on solubility of toluene in water can be studied by constructing a ternary phase diagram.
A ternary phase diagram is a graphical plot showing the conditions under which we get a clear toluene solution.
It has a miscible region and immiscible region.

13. Any combination in the miscible region produces a homogenous and clear solution of toluene in water.
Ternary phase diagrams are used in formulation of elixirs, injections, lotions, etc.

14. PROCEDURE
1) Prepare 20 mL of a mixture of ethanol and toluene with 10% ethanol by transferring 2 mL of ethanol and 18 mL toluene.
2) Fill a burette with water 
3) Titrate the mixture immediately with water until it becomes cloudy. 
4) Record the volume of water used in titration .
5) Repeat step 1 to 4 by using mixture of ethanol and toluene with various ethanol percentages which consists of 25%, 35%, 50%, 65%, 75%, 90%, and 95%.
6) calculate the percentage of each component in the mixture after addition of water.
7) plot the points onto a triangular paper to give a triple phase diagram.

15. Volume ( mL)
Percentage (%)
Initial %
Ethanol
Toluene
Water
Total 10 2 18 25 5 15 35 7 13 50 65 75 90 95 19 1