Measurement and Correlation of the Solubility of Baicalin in Several Mixed Solvents

The baicalin was dissolved in four groups of mixed solvents consisting of organic solvents (methanol, ethanol, n-propanol, and isopropanol) and water in different proportions with the temperature 278.15–318.15 K. The solubility of baicalin at the steady state of the system was measured by static technique under 101.1 kPa. Under the condition of constant temperature, the proportion of organic solvent increased, and the solubility of baicalin increased accordingly; when the ratio of organic solvent was constant, the temperature increased and the mole fraction of baicalin also increased. In the case where the temperature and the ratio of the organic solvent were constant, the mixture of n-propanol and water had an advantage in dissolving baicalin. The solubility of baicalin was calculated by the Jouyban–Acree model, the van't Hoff–Jouyban–Acree model, and the Apelblat–Jouyban–Acree model. The maximum value of RAD (average relative deviation) in all calculations was 1.63%. It is noteworthy that the solubility data presented in this work contribute to providing the necessary physical and chemical information for the pharmaceutical industry to improve production and purification processes.