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

Two novel crystal forms of bis-(oxonium) ethane-1,2-di-sulfonate, 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 ). 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 mol-ecule 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.