*1.2.1 Melting point*

The temperature at which the solid and liquid phases are in balance determines the melting point, which is a fundamental physical characteristic. The value is calculated using the ratio of the change in fusion enthalpy over the change in fusion entropy because melting point is a thermodynamic process where the free energy of transition is equal to zero [35]. Over a conventional melting point apparatus or the Kofler method, DSC is the preferred approach for getting precise melting point data because it allows for the determination of additional thermal data, such as the enthalpy of fusion [35]. It is a common practice to determine a compound's melting point in order to characterize or identify its purity. However, in the field of pharmaceutical sciences, the melting point also has significant value because of its relationships with water solubility and vapour pressure [21]. Although it was necessary to make assumptions about the entropy of fusion, the melting point has actually been directly connected to the log of solubility [36]. In order to tune an API's aqueous solubility towards a specific purpose, it would be highly helpful to know the melting point of that API before it was synthesized.
