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Three – Component System

The purpose of this experiment is to determine the solubility limits in a system made

up of water and two other liquids, one or both of which are only partially miscible with water 

and to plot the solubility curve of the given three-component system. ight !"-gram solutions

containing #" $, !% $, &" $, and '" $ by weight of acetic acid in water and acetic acid in

 ben(ene were prepared at a constant temperature of !% )C, The solutions were titrated to

cloudiness with ben(ene and with water, respectively. The percent composition of eachcomponent was computed and plotted on a ternary diagram.

1. *ntroduction

+ phase diagram shows the phases existing in equilibrium at any given condition.

+ccording to the phase rule, a maximum of four intensive variables intensive properties

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must be specified to completely define the state of a three-component system. The intensive

variables that are usually chosen are pressure, temperature, and concentration.

or a three-component system at constant pressure and temperature, the solubility

relations of the system can be represented using an equilateral triangle. The percentage of 

each component is represented by the perpendicular distance from the side opposite one apex

to any point on the diagram, and each pure component is represented by each vertex of the

triangle.

2. /aterials and /ethods

2.1 /aterials and +pparatus

The materials used in this experiment are component + water, 0% ml of 

component 1 +cetic acid, and #"" ml of component C ben(ene. The apparatus

used are the thermometer, ! burettes, 2 glass-stoppered bottles %" ml. # %-ml pipette.

2.2 /ethods

Solutions of 3nown concentrations were prepared containing #"$, !%$, &"$,

and '"$ by weight of acetic acid in water. Twenty grams of each solution was

 prepared and placed in a %"-m4 glass-stoppered bottle. + constant temperature of !%

)C was set and the solution was titrated with the third component, ben(ene. The

solution was sha3en vigorously after each addition of the titrant. The end point of the

titration was ta3en to be the first appearance of perceptible cloudiness. Solutions

containing #"$, !%$, &"$, and '"$ by weight of acetic acid in ben(ene were

 prepared. The solutions were titrated to cloudiness with water at a constant

temperature of !% )C.

The percent by weight of each component present at the appearance of the

second phase was calculated and plotted on a ternary diagram. + smooth curve was

drawn through the points.

5n the diagram, a point designated as / lying in the heterogeneous region about

midway between the center of the region and one side of the bounding curve was

selected. + %"-m4 sample, with a composition corresponding to the selected point on

the diagram, was prepared and sha3en vigorously for several minutes. The sample

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was then allowed to stand until two separate layers were formed. 6ith the aid of a

separatory funnel, each layer was run into a weighted flas3. The weight of each

solution was determined to the nearest twentieth of a gram. 5ne ml of water was

added to each sample to determine the water-rich phase. The water-rich solution was

to remain homogeneous after the addition of water and the other is to become

heterogeneous after the addition of water.

3. 7esults