4-Hydroxy-2-methyl-1,1-dioxo-2H-1λ6,2- benzothiazine-3-carboxylic acid hemihydrate

In the title compound, C10H9NO5S·0.5H2O, two geometrically different organic molecules are present. The benzene rings and the carboxylate groups are oriented at dihedral angles of 13.44 (4) and 21.15 (18)°. In both molecules, an intramolecular O—H...O hydrogen bond generates an S(6) ring. In the crystal, both moleucles form inversion dimers linked by pairs of O—H...O hydrogen bonds to generate R22(8) loops. The dimers are consolidated into chains extending along [100] by bridging O—H...O hydrogen bonds from the water molecule. A weak C—H...O hydrogen bond also occurs