4-Carboxy-pyridinium 3-carb-oxy-4-hydroxy-benzene-sulfonate.

Cocrystallization of 4-carboxy-pyridine (4-CPY) and 5-sulfosalicylic acid (5-H(2)SSA) yields the title salt, C(6)H(6)NO(2) (+)·C(7)H(5)O(6)S(-). In the crystal structure, the components of the salt are linked by a combination of inter-molecular O-H⋯O and N-H⋯O, and weak C-H⋯O hydrogen bonds, forming a three-dimensional framework.