The crystal structures of two novel polymorphs of bis­(oxonium) ethane-1,2-di­sulfonate

Two novel crystal forms of bis­(oxonium) ethane-1,2-di­sulfonate, 2H(3)O(−)·C(2)H(4)O(6)S(2) (2−), are reported. Polymorph II has monoclinic (P2(1)/n) symmetry, while the symmetry of form III is triclinic (P [Image: see text]). Both structures display extensive networks of O—H⋯O hydrogen bonds. While this network in Form II is similar to that observed for the previously reported Form I [Mootz & Wunderlich (1970 ▸). Acta Cryst. B26, 1820–1825; Sartori et al. (1994 ▸). Z. Naturforsch. 49, 1467–1472] and extends in all directions, in Form III it differs significantly, forming layers parallel to the ab plane. The sulfonate mol­ecule in all three forms adopts a nearly identical geometry. The other observed differences between the forms, apart from the hydrogen-bonding network, are observed in the crystal density and packing index.