What is "arsenic acid"

n. (context inorganic compound English) 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.

n. an acid formed from arsenic pentoxide

Arsenic acid is the chemical compound with the formula HAsO. More descriptively written as AsO(OH), this colorless acid is the arsenic analogue of phosphoric acid. Arsenate and phosphate salts behave very similarly. Arsenic acid as such has not been isolated, but only found in solution where it is largely ionized. Its hemihydrate form (HAsO·½HO) does form stable crystals. Crystalline samples dehydrate with condensation at 100 °C.