A triclinic modification of 3,4-dihy-droxy-benzoic acid monohydrate

The unit cell of the title compound, C(7)H(6)O(4)·H(2)O, features four independent formula units; the individual carb-oxy-lic acid mol-ecules themselves are nearly planar (r.m.s. deviations = 0.0189, 0.0334, 0.0356 and 0.0441 Å). Two independent mol-ecules each form two hydrogen bonds by acid-carbonyl O-H⋯O inter-actions and the dimers are also nearly planar (r.m.s. deviations = 0.039 and 0.049 Å). The two independent dimers are aligned at 44.5 (1)°. Other O-H⋯O inter-actions involving the hy-droxy groups and water mol-ecules give rise to a three-dimensional network.