Source : Webster's Revised Unabridged Dictionary (1913)

Disulphate \Di*sul"phate\, n. [Pref. di- + sulphate.] (Chem.)
   (a) A salt of disulphuric or pyrosulphuric acid; a
       pyrosulphate.
   (b) An acid salt of sulphuric acid, having only one
       equivalent of base to two of the acid.