Solubility Measurement and Data Correlation of Metformin Hydrochloride in Four Aqueous Binary Solvents and Three Pure Solvents from 283.15 to 323.15 K

The solubility of form A metformin hydrochloride (MET·HCl) in water, methanol, ethanol, water + methanol, water + ethanol, water + acetone, and water + isopropanol at the temperatures ranging from 283.15 to 323.15 K was determined by gravimetric method. The experimental results show that the solubility increases with the increase of temperature and the initial water content of the binary solvents. The order of solubility in the four aqueous solvent mixtures is water + methanol > water + ethanol > water + isopropanol > water + acetone, which is mainly contributed by the hydrogen bond interactions. The modified Apelblat model, CNIBS/R–K model, and Apelblat–Jouyban–Acree model were used to correlate the solubility data. The results show that the Apelblat model can correlate the solubility of four binary solvents best, and all average relative deviations are less than 6%.