h2s3o6

from The Collaborative International Dictionary of English v.0.48

Trithionic \Tri`thi*on"ic\, a. [Pref. tri- + thionic.] (Chem.)
   Of or pertaining to, or designating, a certain thionic acid,
   {H2S3O6} which is obtained as a colorless, odorless liquid.
   [1913 Webster]