Pyrosulphuric

Pyr`o`sul`phu´ric


a.1.(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.
Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.