Source : Webster's Revised Unabridged Dictionary (1913)

Bisulphate \Bi*sul"phate\, n. [Pref. bi- + sulphate.] (Chem.)
   A sulphate in which but half the hydrogen of the acid is
   replaced by a positive element or radical, thus making the
   proportion of the acid to the positive or basic portion twice
   what it is in the normal sulphates; an acid sulphate.