Abnormal desolvation behavior on solvate of etodolac sodium salt

Sodium salts of (+/-)- and (+)-etodolac were prepared and characterized: the (+/-)-sodium salt contained 5.26% water and 1.09% acetonitrile, and the (+)-sodium salt contained 1.14% water and 2.02% other volatiles (methanol and acetonitrile). Abnormal hygroscopic behavior of the (+/-)-etodolac sodium salt was observed; that is, it lost weight (5.4%) at 75% RH for 7 days. A possible reason for the abnormal hygroscopic behavior is nucleation phenomenon at the interface; that is, a surface change may occur in the presence of water vapor with nucleation by small crystals of the product.