-hyposulphuric-

a. [ Pref. hypo- + sulphuric. ] (Chem.) Pertaining to, or containing, sulphur in a lower state of oxidation than in the sulphuric compounds; as, hyposulphuric acid. [ 1913 Webster ]

Hyposulphuric acid, an acid, H2S2O6, obtained by the action of manganese dioxide on sulphur dioxide, and known only in a watery solution and in its salts; -- called also dithionic acid. See Dithionic. [ 1913 Webster ]