Form I, form II, and CHCl3-II type of acetohexamide are obtained by recrystallization from different solvents. X-ray diffraction patterns, infrared spectra, and differential scanning calorimeter curves of the CHCl3-II type are identical with those of form II, but CHCl3-II type contains a chloroform molecule, which cannot be removed by normal drying condition, and CHCl3-II type seems unsuitable for medical use. The solubility of form II is 1.2 times that of form I.
