The Collaborative International Dictionary
Pyrosulphuric
Pyrosulphuric \Pyr`o*sul*phu"ric\, a. [Pyro- + -sulphuric.] (Chem.) Pertaining to, or designating, an acid called also disulphuric acid) obtained by distillation of certain sulphates, as a colorless, thick, oily liquid, H2S2O7 resembling sulphuric acid. It is used in the solution of indigo, in the manufacture of alizarin, and in dehydration.
Wiktionary
pyrosulphuric
a. (context British English) (alternative spelling of pyrosulfuric English)