Columnar crystals of 6-hydroxy-2-naphthoic acid and process for manufacturing the same

摘要

A process for manufacturing columnar crystals of 6-hydroxy-2-naphthoic acid comprising the steps of, dissolving crude 6-hydroxy-2-naphthoic acid product in an aqueous solvent, adding crystalline 3-hydroxy-2,7-naphthoic acid or columnar crystals as seed crystals, and cooling the mixture to precipitate the desired crystals. The present invention further provides columnar crystals of 6-hydroxy-2-naphthoic acid which have X-ray diffraction peaks 2theta in 16.8-17.8 and/or 21.3-22.3.