Solubility and Pseudo Polymorphic Behavior of Nicotinic Acid in Alcoholic Solutions: Experimental Data and Phase Equilibrium Modeling

Nicotinic acid is an organic component with applications in different industrial processes. Separation, purification, and the development of new products based on this material depend on solid–liquid equilibrium data. The application of mathematical models is useful for the development of solution theories and process simulators. Excess thermodynamic properties are fundamental to evaluate the deviation from ideality present in a solution. Thus, the current work presents the study of solubility and excess solubility of nicotinic acid in binary liquid solutions formed by water + methanol and water + ethanol, covering the entire range of molar composition of the binary liquid mixture at temperatures ranging from 293.15 to 323.15 K. Equilibrium between solid and liquid phases was described by the PC-SAFT and CPA equations of state and the NRTL activity coefficient model. Regarding solubility, the existence of maximum and minimum points were observed indicating a possible solvation effect in both mixtures. Excess solubility calculations also indicate solutions with a high deviation from ideality. All models used have been able to successfully correlate the solubility results.