METHOD OF EVALUATING EVENNESS OF SUPLATAST TOSILATE CRYSTAL, EVEN CRYSTAL, AND PROCESS FOR PRODUCING THE SAME

摘要

A method of evaluating the evenness of suplatast tosilate crystals; and stable crystals having evenness in optical purity. The method of evaluating the evenness of suplatast tosilate crystals is characterized by comprising (a) a step in which a solvent is added to the suplatast tosilate crystals to dissolve up to 3% of the crystals and part of the supernatant of the resultant suspension is taken out and examined for optical purity and (b) a step in which a solvent is then added to the remaining suspension to dissolve the whole crystals and part of the solution is taken out and examined for optical purity, and by comparing the optical purity obtained in the step (a) with that obtained in the step (b). Suplatast tosilate crystals excellent in evenness and thermal stability are provided.