AbstractThe enantiomers of iopanoic acid were purified by crystallization and characterized by optical rotation, DSC, IR spectra, X‐ray powder diffraction, and chiral HPLC. (‐R)‐enantiomer: [α]20D = −6.1°, mp. = 165.4°C; (+S)‐enantiomer: [α]20D = + 6.2°, mp. = 165.6°C. The IR spectra and X‐ray patterns are fingerprints. Chiral HPLC (isocratic method, mobile phase: ethanol/n‐hexane, 2/98 with 0.5% acetic acid) gave a resolution = 0.98 and a 99.6% recovery.From X‐ray and thermal analyses the racemate FormI, mp. = 153.8°C, resulted to be a racemic compound. The binary phase diagram between the enantiomers and the racemic compound was constructed from the phase transition temp. obtained by DSC heating curves of appropriate mixtures. At a given enantiomer ratio (71/29) a eutectic compound, mp. = 144.7°C, is formed. In the range 88–100% a solid solution between t