The Collaborative International Dictionary of English v.0.48:

Sulphantimonic \Sulph*an`ti*mon"ic\, a. [Sulpho- + antimonic.]
   (Chem.)
   Of, pertaining to, or designating, a hypothetical sulphacid
   of antimony (called also thioantimonic acid) analogous to
   sulpharsenic acid.
   [1913 Webster]