![ternary diagram acetic acid water 1-butanol ternary diagram acetic acid water 1-butanol](https://d3i71xaburhd42.cloudfront.net/adb6e2fa0319c9dbf0d8cacb60ef5c4c6ff18bba/4-Figure4-1.png)
Thus only the 1-butanol mass fraction in phase 1, temperature and pressure are required for complete description of the system, which had separated into two phases. Given the point ’A’ in figure 1 (depending on the 1-butanol mass fraction in phase 1), the points ’B’ and ’C’ are uniquely determined. If the system was initially in the two-phase region, the tie line uniquely connects the points along the phase separating line. Hence the phase rule holds with f = 5 − p = 3 (i.e., mass fraction for 1-butanol, temperature and pressure).
![ternary diagram acetic acid water 1-butanol ternary diagram acetic acid water 1-butanol](https://ars.els-cdn.com/content/image/1-s2.0-S0378381219303826-gr8.jpg)
This determines the mass fractions for water and acetic acid. Note that in the figure 1 only the mass fraction of 1-butanol must be given when the system remains on the phase boundary line. A graphical demonstration and an interpretation of a tie line are given in figure 1.
![ternary diagram acetic acid water 1-butanol ternary diagram acetic acid water 1-butanol](http://4.bp.blogspot.com/-nzFkQTcl58I/VmPRDe3UyDI/AAAAAAAAACM/Z1O-WFcyaN4/s280/phase%2B2.jpg)
The tie line must also contain the point describing the overall system composition. The compositions of the phases that form are given by the intersections of a tie line with the phase boundary. If the three components are mixed to give an overall system composition that falls in the 2-phase region, the system will separate into two phases: a phase rich in water and another rich in 1-butanol. Sometimes it is easier to see this when stopping the stirring briefly. The turbidity results from scattering of light by the large number of very small “oily” droplets of the second phase that are produced when the system is stirred. When the solution is stirred, the transition from one region to another can be observed by appearance (or disappearance) of cloudiness or turbidity in the solution. Note that the line drawn is hypothetical, the real curve will be determined in this experiment. Regions where one or two phases appear have also been indicated in figure 1. This graph accounts for the fact that only two variables are required and along the phase boundary only one variable is required. The one- and two-phase regions have been separated by a black line.