Bis(tetra­methyl­amonium) bis­(2,4,5-carboxy­benzoate)–benzene-1,2,4,5-tetra­carboxylic acid (1/1)

The asymmetric unit of the title compound, 2C(4)H(12)N(+)·2C(10)H(5)O(8) (−)·C(10)H(6)O(8), consists of a tetra­methyl­amonium cation, an anion derived from the singly deprotonated pyromellitic acid anion, 2,4,5-carboxy­benzoate (H(3)bta(−)), and one-half of a benzene-1,2,4,5-tetra­carboxylic acid (H(4)bta) mol­ecule, which has the centroid of the aromatic ring positioned at a crystallographic centre of inversion. The H(4)bta and H(3)bta(−) residues are involved in an extensive inter­molecular O—H⋯O hydrogen-bonding network, which leads to a three-dimensional supra­molecular structure containing one-dimensional channels running parallel to the [001] crystallographic direction. These channels house the tetra­methyl­amonium cations.