What is "disulphuric acid"

Disulphuric \Di`sul*phu"ric\, a. [Pref. di- + sulphuric.] (Chem.) Applied to an acid having in each molecule two atoms of sulphur in the higher state of oxidation.

Disulphuric acid, a thick oily liquid, H2S2O7, called also Nordhausen acid (from Nordhausen in the Harts, where it was originally manufactured), fuming sulphuric acid, and especially pyrosulphuric acid. See under Pyrosulphuric.

n. (context chemistry English) A thick oily liquid, H₂S₂O₇.