arsenic acid

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

• noun A poisonous, hygroscopic, white, translucent crystalline compound, H₃AsO₄, occurring chiefly in its hemihydrate form, used to manufacture arsenates and glass, and in treating wood.

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

• noun inorganic chemistry A poisonous, white crystalline compound, H3AsO4, formed from arsenic pentoxide and water; it has the same structure as phosphoric acid, and is used in the manufacture of arsenates.

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

• noun an acid formed from arsenic pentoxide