The Collaborative International Dictionary of English v.0.48:

Sulphydrate \Sul*phy"drate\, n. (Chem.)
   A compound, analogous to a hydrate, regarded as a salt of
   sulphydric acid, or as a derivative of hydrogen sulphide in
   which one half of the hydrogen is replaced by a base (as
   potassium sulphydrate, KSH), or as a hydrate in which the
   oxygen has been wholly or partially replaced by sulphur.
   [1913 Webster]