Simple and Green Experimental Design for Physical Chemistry Lab: Two-Part Solid-Phase Equilibrium System with Simple Eutectic Point

The purpose of this study is to provide an alternative design for the phase equilibrium experiment of naphthalene-diphenyl amine system, etc. in the Physical Chemistry Laboratory course with a green chemistry approach. In this proposed method, palmitic acid-pentadecanoic acid system has been used. The phase equilibrium diagram of this system shows a simple eutectic point. The proposed system, unlike solid-phase equilibrium systems - common liquid in physical chemistry lab, not only does not have environmental problems and is not harmful to human health, but its waste materials can be easily recycled. After reviewing the results, the melting point of 66.4 °C for palmitic acid and 60.3 °C for pentadecanoic acid was obtained. Then, the adaptation of the experimental data was performed with the proposed polynomials of Excel software and the enthalpy of melting of palmitic acid was determined as 60.85 kJ per mole. Also, the  eutectic point was observed around 57 °C and molar fraction 0.44 for palmitic acid.