Hydrazine-1,2-diium bis­(3-carb­oxy-4-hy­droxy­benzene­sulfonate) tetra­hydrate

Reaction of 5-sulfosalicylic acid with hydrazine hydrate at pH = 1 results in the formation of the title hydrated salt, 0.5N2H6 2+·C7H5O6S−·2H2O. The hydrazinium dications lie on centres of inversion. They are located between 3-carb­oxy-4-hy­droxy­benzene­sulfonate anions, forming inter­molecular N—H⋯O hydrogen bonds with sulfonate ions and water mol­ecules of crystallisation. Further intra- and inter­molecular O—H⋯O hydrogen bonds are observed in the crystal structure