title: 2,3,4-Trihy-droxy-benzoic acid 0.25-hydrate.
abstract: The asymmetric unit of the title compound, C(7)H(6)O(5)·0.25H(2)O, contains two mol-ecules of 2,3,4-trihy-droxy-benzoic acid, with similar conformations, and one water mol-ecule which lies on a twofold rotation axis. Both acid mol-ecules are essentially planar [maximum r.m.s deviations = 0.0324 (2) and 0.0542 (3) Å for the two acid molecules]. The mol-ecular conformations are stabilized by intra-molecular O(phenol)-H⋯O(carbox-yl/phenol) inter-actions. A cyclic inter-molecular association is formed between the two acid and one water mol-ecule [graph set R(3) (3)(12)] involving O-H⋯O hydrogen bonds. The two acid mol-ecules are further linked through a cyclic R(2) (2)(8) carb-oxy-lic acid hydrogen-bonding association, which together with inter-molecular O-H⋯O hydrogen-bonding inter-actions involving the phenol groups and the water mol-ecule, and weak π-π inter-actions [minimum ring centroid separation = 3.731 (3) Å], give a three-dimensional network.
authors.affiliation: Guangdong Province Key Laboratory of Pharmacodynamic Constituents of, Traditional Chinese Medicine and New Drugs Research, Institute of Traditional Chinese Medicine and Natural Products, Jinan University, Guangzhou 510632,  People's Republic of China.
authors.forename: Jin-Hang
authors.initials: JH
authors.lastname: Li
authors.forename: Fu-Yue
authors.initials: FY
authors.lastname: Dong
authors.forename: Fang
authors.initials: F
authors.lastname: Cai
authors.forename: Xiao-Feng
authors.initials: XF
authors.lastname: Yuan
authors.forename: Ren-Wang
authors.initials: RW
authors.lastname: Jiang