# Determination of the Solid-Liquid Phase Diagram for Napthalene-Biphenyl Using Thermal Analysis

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Experiment #1: Determination of the Solid-Liquid Phase Diagram for Napthalene-Biphenyl Using Thermal Analysis

Objective

To apply thermal analysis to the two-component system, naphthalene-biphenyl at atmospheric temperature. The analysis will be represented by a solid-liquid phase diagram (freezing point diagram).

Theoretical Principles
Phase Equilibria and the Gibbs Phase Rule

This experiment is conducted in order to study a condensed system (solid-liquid) at constant temperature (atmospheric temperature). It should be noted that the atmospheric pressure is unlikely to be the equilibrium pressure for the system. However, equilibria in condensed systems are not very sensitive to pressure.

The freezing point is determined at
The temperature of the cooling bath must be adjust so that it is always about 3oC below the temperature of the contents.
4. Remelt the contents of the tube and add the counterpart component based on the given schedule. Ask the demonstrator to adjust the cooling water between mixtures. During the experiment, record and plot the data obtained for all mixtures listed. The experiments are stopped as follows:
i. Mixtures 1, 5, 8 – when plateau is reached ii. All others – when the initial change in slope can clearly be identified
5. Draw the SL diagram for naphthalene-biphenyl with ToC as the y-axis, and wt % as the x-axis.
Results and Discussion

Results
Mixture 1
Refer to Figure 1: Mixture 1
By observation, the freezing point is determined to be 80.5oC.
In comparison to the pre-lab data,

Mixture 3
Refer to Figure 2: Mixture 3
It is suspected that the freezing point is 64.1oC. Due to the short temperature plateau, It is difficult to determine if the freezing point occurs at during the interval (6:00-6:10). However, it appears to be have been the most reasonable determination for freezing point in comparison to the rest of the plot.
In comparison to the pre-lab data,

Mixture 4
Refer to Figure 3: Mixture 4
By observation, the freezing point of this mixture is 51.6oC.
In comparison to the pre-lab data,

Mixture 5
Refer to Figure 4: Mixture 5
Due to the lengthy plateau, the freezing point is determined to be 69.1 oC.