pyrosulphuric

from The Century Dictionary.

• Obtained from sulphuric acid by the action of heat.

from the GNU version of the Collaborative International Dictionary of English.

• adjective (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.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective UK Alternative spelling of pyrosulfuric.