perchloric acid

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

• noun A colorless, corrosive liquid, HClO₄, explosively unstable under some conditions, that is a powerful oxidant used as a catalyst and in explosives.

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

• noun A clear colourless liquid; a strong acid and a violent, sometimes explosive, oxidizing agent
• noun chemistry HClO4, the oxyacid of chlorine in which chlorine has the highest oxidation number

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

• noun a powerful oxidizing agent; forms perchlorates