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, 2H₃O^-·C₂H₄O₆S₂ ^2-, are reported. Polymorph II has monoclinic (P2₁/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.