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|Section2= |Section3= |Section7= |Section8= }} Arsenic acid is the chemical compound with the formula H3AsO4. More descriptively written as AsO(OH)3, 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 (H3AsO4·½H2O) does form stable crystals. Crystalline samples dehydrate with condensation at 100 °C. ==Properties== It is a tetrahedral species of idealized symmetry ''C3v'' with As–O bonds lengths ranging from 1.66 to 1.71 Å. Being a triprotic acid, its acidity is described by three equilibria: :H3AsO4 + H2O H2AsO + H3O+ (''K''1 = 10−2.19) :H2AsO + H2O HAsO + H3O+ (''K''2 = 10−6.94) :HAsO + H2O AsO + H3O+ (''K''3 = 10−11.5) These ''K''a values are close to those for phosphoric acid. The highly basic arsenate ion (AsO) is the product of the third ionization. Unlike phosphoric acid, arsenic acid is an oxidizer, illustrated by its ability to convert iodide to iodine. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Arsenic acid」の詳細全文を読む スポンサード リンク
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