pyrosulphuric \pyr`osulphu"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.
   1913 webster
see also:
disulphuric h2s2o7 

disulphuric \di`sulphu"ric\, a. pref. di- + sulphuric.
   chem.
   applied to an acid having in each molecule two atoms of
   sulphur in the higher state of oxidation.
   1913 webster

   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.
      1913 webster
see also:
disulphuric acid h2s2o7 nordhausen acid fuming sulphuric acid pyrosulphuric acid pyrosulphuric