Silicofluoric acid

from The Collaborative International Dictionary of English v.0.48

Fluosilicic \Flu`o*si*lic"ic\, a. [Fluo- + silicic: cf. F.
   fluosilicique.] (Chem.)
   Composed of, or derived from, silicon and fluorine.
   [1913 Webster]

   {Fluosilicic acid}, a double fluoride of hydrogen and
      silicon, {H2F6Si}, obtained in solution in water as a sour
      fuming liquid, and regarded as the type of the
      fluosilicates; -- called also {silicofluoric acid}, and
      {hydrofluosilicic acid}.
      [1913 Webster]

from The Collaborative International Dictionary of English v.0.48

Silicofluoric \Sil`i*co*flu*or"ic\, a. (Chem.)
   Containing, or composed of, silicon and fluorine; especially,
   denoting the compounds called silicofluorides.
   [1913 Webster]

   {Silicofluoric acid} (Chem.), a compound of hydrofluoric acid
      and silicon fluoride, known only in watery solution. It is
      produced by the action of silicon fluoride on water, and
      is regarded as an acid, {H2SiF6}, and the type and origin
      of the silicofluorides.
      [1913 Webster]