perchromic

from The Century Dictionary.

• Noting an acid, a substance known only in solution, produced by the interaction of chromic acid and hydrogen dioxid. It is very unstable, of an intense blue color, and probably has the composition H₂Cr₂O₈, analogous to that of persulphuric acid.

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

• adjective (Chem.) Pertaining to, or designating, a certain one of the highly oxidized compounds of chromium, which has a deep blue color, and is produced by the action of hydrogen peroxide.