The Collaborative International Dictionary of English v.0.48:

Sulphantimonious \Sulph*an`ti*mo"ni*ous\, a. (Chem.)
   Of, pertaining to, or designating, a hypothetical sulphacid
   of antimony (called also thioantimonious acid) analogous to
   sulpharsenious acid.
   [1913 Webster]