The Collaborative International Dictionary of English v.0.48:

Sulphite \Sul"phite\, n. [Cf. F. sulfite. See Sulphur.]
   1. (Chem.) A salt of sulphurous acid; -- called also
      sulfite.
      [1913 Webster]

   2. A person who is spontaneous and original in his habits of
      thought and conversation. [Archaic Slang] --
      Sul*phit"ic, a. [Slang]

            A sulphite is a person who does his own thinking, he
            is a person who has surprises up his sleeve. He is
            explosive.                            --Gelett
                                                  Burgess.
      [Webster 1913 Suppl.]