Physicochemical characteristics of crystalline water of (RS)-7-(2-amino-methylmorpholino)-1-cyclopropyl-6, 8-difluoro-1, 4-dihydro-4-oxo-3-quinoline-carboxylic acid were studied by thermal analyses and powder X-ray diffractmetry. The dihydrate of the compound was stable under ambient or humidified conditions. The dihydrate converted to a monohydrate on drying under mild conditions. The mono-and dihydrates transformed into α-type anhydrate at 110°C. These three kinds of crystals were convertible each other under appropriate conditions. At 165°C, the hydrates and the α-anhydrate converted to β-type anhydrate. The compressed effects on the crystalline waters were also discussed for the dihydrate by kinetic analyses.
