Disodium 4,5,6-trihy­droxy­benzene-1,3-disulfonate dihydrate

In the title compound, 2Na(+)·C(6)H(4)O(9)S(2) (2-)·2H(2)O, the benzene rings of the 4,5,6-trihy-droxy-benzene-1,3-disulfonate ions, which are stacked parallel to each other forming rods parallel to the a axis, are slightly deformed (planarity, symmetry) mainly because of the high degree of substitution. The two sodium ions, located within pockets of the anion rods, are coordinated by six and seven O atoms, resulting in octa-hedral and penta-gonal-bipyramidal coordinations, respectively. In addition to these coordinative bonds towards sodium, an extended network of intra- and inter-molecular hydrogen bonds occurs.