This approach is used in the formulation of solutions. 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. However, if it is soluble in both of the liquids, the mutual solubility is increased. If this third component is more soluble in one of the two different components the mutual solubility of the liquid pair is decreased. The addition of a third component to a pair of miscible liquids can change their mutual solubility. If we follow the convention given above (lights at the top, heaviest and mediums at the sides), the two-phase region will be found at the top. Inside the binodal curve or phase envelope, the two phase condition prevails.

The binodal curve is the boundary between the two-phase condition and the single-phase condition. There will be different envelopes (binodal curves) at different pressures and temperatures. To differentiate within the two-phase region and single-phase region in the ternary diagram, pressure and temperature must be fixed. At the very center of the triangle, we find 33.33 % of each of the component.

As you move from one side (0 %) to the 100 % or pure condition, the composition of the given component is increasing gradually and proportionally.On any of those sides, the fraction of the third component is zero (0%).Each side of the triangle represents all possible binary combinations of the three components.

Hence, at the top we have 100 % B, and at each side, 100 % A and 100 % C, respectively. Every corner represents a pure condition.The heavy and medium components are placed at the left hand corner (B) and right hand corner (C), respectively. By convention, the lightest component is located at the apex or top of the triangle (A).Any point within this triangle represents the overall composition of a ternary system at a fixed temperature and pressure.Note that the relationship among the concentrations of the components is more complex than that of binary systems.ДЇigure 1 : Three - component triangular representation Figure 1 shows an example of a ternary phase diagram. In modern times, we use an equilateral triangle for such a representation. This irregular triangle is often transformed into an equilateral triangle to facilitate presentation and interpretation. The actual ternary diagram may be represented as a three dimensional form or more commonly as a two dimensional projection of the liquids surface onto the base of the triangle created when the three binary diagrams are joined together. Ternary diagrams have a vertical temperature axis. To construct a ternary diagram it is necessary to know the three binary systems for the three components. Ternary phase diagrams are three component systems. Gibbs first proposed the use of a triangular coordinate system. A rectangular coordinate plot, having only two axes, will no longer suffice. Intuitively, having more than two components poses a problem when a pictorial representation is desired. For example, air is often approximated as being composed of nitrogen, oxygen, and argon, while dry natural gas can be rather crudely approximated as being composed of methane, nitrogen and carbon dioxide. Ternary systems are more frequently encountered in practice than binary systems. Ternary or three-component system is a complex type of multi- component system.

OBJECTIVE: To determine phase diagram for three component system (ethanol/ toluene/ water system theory) TITLE: Determination of Phase Diagram for Ethanol/ Toluene/ Water System Theory

Two phase region ternary diagram