h2wo4

from The Collaborative International Dictionary of English v.0.48

Tungstic \Tung"stic\ (t[u^]ng"st[i^]k), a. (Chem.)
   Of or pertaining to tungsten; derived from, or resembling,
   tungsten; wolframic; as, tungstic oxide.
   [1913 Webster]

   {Tungstic acid}, an acid of tungsten, {H2WO4}, analogous to
      sulphuric and chromic acids.
      [1913 Webster]