Abstract
The title hydrated salt, C6H6NO2 (+)·C10H5O8 (-)·H2O, was isolated from the 1:1 cocrystallization of benzene-1,2,4,5-tetra-carb-oxy-lic acid and isonicotinic acid in ethanol solution. In the crystal, the cation is close to planar [r.m.s. deviation = 0.085 Å for the nine fitted atoms; the C-C-C-O(carbon-yl) torsion angle = -8.7 (4)°], but twists are evident in the anion, with all but the carb-oxy-lic acid group diagonally opposite the carboxyl-ate group being significantly twisted out of the plane of the benzene ring [C-C-C-O(carbon-yl) torsion angles = -118.1 (2), -157.6 (2), 4.3 (3) and 77.3 (3)°]. In the crystal, the ions and water mol-ecules are consolidated into a three-dimensional architecture by O-H⋯O and N-H⋯O hydrogen bonding along with C-H⋯O inter-actions.