vanadic acid

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An acid containing a vanadate group, especially HVO₃, H₃VO₄, or H₄V₂O₇, not existing in a pure state, but often used in its anhydride form, vanadium pentoxide.

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

• noun chemistry any of various hydrated forms of vanadium pentoxide

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun any of various oxyacids of vanadium; known mostly in the form of its salts